I'm happy that Sigfried can now let me pick him up for about 20 seconds without wiggling too much (we're making progress, I tell ya) but... his emptying his anal glands

on my arm isn't too encouraging (sorry for those who were eating).This is the second time he does this - and sometimes he just smells. I know it's nothing to worry about, but how common is this? I know of many cats who never did this. Am I just too clumsy and my cat too wiggly?
What can I do about it? I'll try not to ...push that button... but isn't he supposed to clean them himself or something? I'm not too sure I want to do it myself, though. Bleah.