Oh, don't beat yourself up over it! One day won't trigger the end of the world, he might be a little itchy, but his bits won't fall off because of it ;)
My guys can get pretty antsy-pants'd when I clean them out too. Usually I plant myself firmly against their hip (JUST in case they decide to throw a kick) and tell them 'Loki/Red/Divo hold still
. Almost done.' in a firm but soothing voice. Sometimes I just go up there using water as a lubricant, get the bean, get out, then come back the next day to finish it all up with some KY.
Loads of treats at the end, of course. Divo had three lima bean sized chunks
stuck in his you-know-what. I got one out by just goin' up in there, and then the other two when he relaxed and dropped the next day. That was an experience XD he wasn't haltered and wasn't tied, just "THERE IT IS! GRAB HOLD!"