I would clean him with a wet rag until you can talk to the vet. If you use a razor on him it will make him itchy. When our little girl, Trixie (12), gets the runs I take her to a local groomer (actually it is a vet office that also has grooming) and they use small clippers and clip her bottom. I can't use scissors and clip her becuase she is too thin. She has no fat or muscle so I'm afraid I'll hurt her if I try. I hope your kitty feels better soon.