I have a new kitten (now ~8 weeks old) who does not always do the best job cleaning his behind. Is this normal? If not, what can I do to help encourage his good hygiene? Thanks!
He's still pretty young. He may get better with time.
How old was he when you got him? Typically when kittens are removed from mom too soon they can have problems with some basic cat things (like cleaning their bums). Of course, some cats, like some people, are slobs too.
Is he long haired? Is his poo soft? These things can also make otherwise clean kitties subject to a dingleberry or two.
8 weeks is very young, it is completely normal to give a helping butt cleaning after. Some pick it up faster then others, but one thing to remember is mom cat cleans up after them usually. If possible, catch him right after and clean his butt, believe me, he will eventually take over, and very soon!
Neither of mine really got the hang of even attempting to groom themselves anywhere properly until they were around 4 months old, then they started and gradually improved over time. Sonic is now 6 months and has started washing his own face with his paw only recently (so cute!). I don't think many 8 week old kittens clean their own rear end, mum would normally still be doing it for them at that age, so you have to be mum for him until he gets the hang of it.