In terms of cleaning her up, a warm damp washcloth or unscented baby wipes work well. If you go for baby wipes, be very careful about the ingredients - some things are fine for babies, but can be problematic if ingested by a cat. I use a brand called Water Wipes - they're very pure, with nothing that can cause a problem. I know amazon.com has them, but I don't know about other US stockists.
ferocioussamo
is right about butter - a little butter, warmed in your fingers and smeared on/around the butt can prompt a cat to start grooming to get the butter off. If you care for for furniture, it's probably a good idea to confine the cat/kitten to a bathroom or laundry room for a little while after...or cover everything that matters in towels or plastic