Depends on where, what, and number 1, the Top's desires.
If it involves piss, then at least a shirt/top on.
In my perfect world, the only skin contact i want is a cock in my ass, or mouth. Whether both fully clothed, one not does not matter in my perfect world.
In real life, wearing a short - mid-thigh or shorter, dress/skirt, or nude. Back when i cruised the parks, rest areas, bookstores and other venues, button shirt mostly unbuttoned was quicker to take off and more important, quicker to put on than a t-shirt. Short shorts (old nba style), tennis shoes (keys in shoes), in a quart plastic cup, a weak G&T (refill supplies in trunk), 420. On a good day : 0500 - 1500, 1800 if i stayed past 1500 - traffic, but civilians begin showing around four, cell phones with cameras and easily offended so usually gone by 3. Unless i was busy.
Homes and hotels, nude or a dress, go with the flow. Sometime a jock, panties, chastity, to make sure my role is unmistakably bottom.