A little thong ideally and preferably one that creates a nice bulge with very little space for gunge inside. Think Joe Synder or Koala.. Failing which any tight swimwear, a singlet or anything designed to add to the humiliation. My all time favourite humiliating outfit being the bunnyboy costume with bow tie, cuffs, ears snd a cute little fluffy tail.
Gunge combo would be eggs cracked over the head, pies to the face, lots of thick treacle and finished off with a bag of flour.
Scene would be having the above done to me in the bunnyboy costume in a bar or club with people watching, laughing and not quite believing what's happening to me.