TG: no, I don't wear underpants (when cycling). I might try, as part of a programme of permuting random things. JOOI, do _you_ do anything aimed at avoiding chafing?
I sometimes put a big dollop of Savlon on my nether regions. Like Charlotte says, be generous and put plenty on. It works it's way in. I've done it when I've been sore and it has cured it before.
I wear DHB shorts at the moment and they feel abrasive after about 2-300km, but I'll keep using them because it should toughen me up a bit. Once I get my leather scrotum I have no trouble. I think you do toughen up to it after a while.
I find Lusso shorts more comfortable. Different shorts do make a difference.
Cleaning is a good idea too.
I wouldn't reccommend trying underpants though.