I'd worry about your amp. Electrical circuits are notorious for not liking water. Naphtha will clean off your bass alright, as Shodan pointed out. A dry cloth (or even clean paper towels from the men's room) will soak up the moisture on your bass, which isn't as dangerous as the following. Not to be gross, but when you think about how much sweat, dust and who-knows-what is in the air in most bars and that lots of it touches your instrument for hours each gig, you should disinfect it before you bring it back into your house. Even cases left open at gigs end up with contaminants absorbed into the lining. (I had a case that stunk so bad I had to get rid of it. The guitar that was in it was okay.) Why do you think finishes change colors after so many years? What's that doing to your lungs? No wonder musicians die young.