Well, everyone has a preference for what underwear (if any!) they prefer on the guy they're going to spank. Naturally the underwear will be coming down and or off as the spanking progresses.
As Hardhand correctly notes, my own preference is for white jockey-style briefs. But there IS a compromise which I feel is even more erotic than either boxer briefs or regular briefs. Abercrombie & Fitch make mens' briefs which, unlike the usual medium-to-high-cut leg opening of briefs, have a VERY short "leg" -- only about an inch long. I feel this actually accentuates the butt, giving just enough extra material to cling to the area where the ass juts out from the thighs.
Regular boxer briefs, to my thinking, tend to make the butt look too shapeless, "blending" it into the thighs because of the long legs on that type of underwear. I also feel boxer briefs are not as effective in acting as a restraint when they're pulled down. The extra material allows a lot more movement.
Ideally, I have found over time, the perfect briefs for a guy to be spanked in (and on!) are the A&F mens' white cotton briefs -- in a size one size smaller than the guy would normally wear. For instance if a guy buys jeans with a 34" waist, the briefs should be size 32". This makes them fit and conform very snugly to the ass. Because of the elastic waistband, they won't appear "too small" either. And due to the particular way these briefs are constructed, they show a nice bulge (viewed from the rear between spread legs) of the spankee's balls.
There are a few other "favorites" I have, for different situations. I don't like "bikini" briefs much, since they tend to look silly except on an 18-year-old in perfect physical shape. But different types and or brands of briefs look better on some guys than on others, because of the "type" of ass the guy has.
I classify spankee's butts in four major categories: the round slightly plump "bubble butt" which is so popular; the more elongated leaner butt that has a very gradual slope out from the back and then a very pronounced "jut" above the thighs; what I call the "cupcake"-style ass, muscular, compact but usually very round and tight and almost-always with a pronounced "dimple" in the side of each cheek; and finally the puffy well-upholstered butt of the guy who is somewhat overweight. Different briefs set off each different style of backside.
The "bubble butt" looks best in regular-cut (sometimes called "full cut") briefs, again, one size too small. The leg openings are not cut too high on these briefs, so there's enough fabric to allow only the slightest peek of "cheek" at the base of each leg. On the lean, longer type of behind, I prefer a "slim cut" or "high cut" brief type. The higher leg openings accentuate the ass covered in the white fabric. For tje "cupcake" style ass (which happens to be my personal favorite) I strongly prefer briefs which have a center seam sewn up the seat -- there are several imported brands with that feature. The tight muscular look is enhanced by the center seam separating and accentuating the cheeks. And finally for the puffy ass, Again I prefer full-cut briefs, but in the thinnest fabric available, which is usually nylon or a Spandex blend. Specifics? Here they come:
For the puffy ass, I recommend the "Winner" house-brand of briefs sold by Target department stores. There's a lot of Spandex in them and the material is fairly thin. For the "cupcake" butt, try Beaufort briefs from France. They have a tight center-seam up the seat, and a horizontal fly instead of the traditional "inverted 'Y'" opening. The legs are cut about medium height, too, allowing those side dimples to show a bit. For the lean, longer behind, the Abercrombie briefs mentioned above work best; helping to accentuate the ass in the way it usually juts sharply out from the thighs. And for the bubble-butt, your best bet is a traditional medium-cut brief; Calvin Klein's are popular, but I think Ralph Lauren Polo briefs are a better cut, and best of all (if you can get them) are Brooks Brothers briefs. All cotton briefs are made of a fabric called "jersey knit" and Brooks Brothers' briefs use jersey cut on the bias before sewing, which makes them cling closely without appearing in any way to be "tight."
Another reason I don't favor boxer briefs, is that I sometimes like to do an intermediate "wedgie" spanking before going on to a full bareass spanking. With briefs, by tugging sharply on the center of the waistband in the rear, you can force the material to gather and bury itself in the guy's butt-crack, almost like a thong, so a lot of bare cheek is showing and vulnerable on both sides. You can't do that with boxer briefs.
Plain boxers I don't care for at all. They almost always render the butt totally shapeless. Navy-issue boxers are kind of hot, but hard to get. They fit a lot more closely than regular boxers, and are made of a material like that of an inexpensive cotton dress shirt, fairly thin. Silk boxers, in my experience, aren't a good idea either. Anythiing you use to spank tends to glance off or slide off the slippery surface, and they bunch up more than any other kind of underwear.
Some spankers who are hoping to make their spankee come during the spanking are drawn to silk boxers, on the theory that the sensation will be more pronounced and erotic sliding around on that silk. Forget it -- to the highly-sensitive underside of an erect _c_o_c_k_, silk feels quite scratchy and uncomfortable, when rubbed on it while pressed down tightly. If you want the guy to come and you want some help from his underpants, you're going to have to do some modifications yourself. Fake fur, the softer and plusher, the better, is a good bet for lining the pouch of his briefs. A good quality "napped" cotton flannel will work well, too. Don't try velvet -- it may feel soft to your hand but to a dick it feels like sandpaper!
You can do amusing things with briefs, too, if you have the time and energy. For one spankee, I sewed on circles of black material onto the seat with a round-dot "bullseye" in the middle to make his underpants look like a target. For another, I slashed the whole seat of the briefs longwise, in very close cuts, with a razor-blade, so that as I spanked him the slashed briefs would slowly be reduced to tatters, exposing more and more bare ass as the spanking progressed.
If you want to get a little more technologically-sophisticated, you can liberally spread the inside of the seat of a pair of briefs with Capsaicin ointment. It has very little odor. The active ingredient is the same stuff which makes hot peppers "hot," although the ointment is stronger than any hot pepper! Within a minute or so of putting on the briefs, your spankee will begin to notice a distinct tingling on his ass, which will gradually increase to a feeling of unpleasantly-burning sting. Assisted by the sting from your hand or paddle, this method makes a spanking atop briefs a MUCH more intense experience than usual. Just be careful to wash your hands thoroughly after applying the stuff -- if you accidentally touch your face or eyes, or hold your _c_o_c_k_ to pee, without washing it off first -- yikes! MAJOR pain!
I have known guys with other very specific fetishes about this kind of thing. One friend kept a drawer full of brilliant-yellow Speedo Lycra racing swimsuits in all sizes, to put on "boys" for the initial stage of their spanking. Another liked to cut the legs off of sheer black ladies' pantyhose and make his spankee were tha "panties" which remained. Too effeminate for my taste. And I have several friends who like the look of a spankee in a jockstrap. I used to like that, when they wore the slim-banded "swimmer's jocks," but those are mostly unobtainable now, and all one can get are the regular jocks with the very wide waistband.
No matter what you choose, the best part is peeling that underwear down to begin the bare-ass spanking itself, the "main event." The spankee can feel his last thin "protection" being taken down, leaving his butt completely vulnerable, and he's also aware of the fabric partly restraining him from struggling or "escaping." And for the spanker, there's a nice visual component -- the high contrast provided as you peel that bright white cotton down, to reveal glowing rosy-red asscheeks which are ready to have their color brightened and deepened even more.
I
guess that's about it, for now, on the matter of briefs.
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