Spray brake cleaners do a great job of flushing greasy junk away. The nice part is that they dry very fast. From CRC to store brands I'v never found one that works best. All do a good job.

I have never had a problem with paint. Someone probably has and I guess you should try it on a hidden piece.

The main thing that I would worry about is flushing crap where you don't want it. If you have a nasty rear cassette in hand, blast away. If it's still on the wheel I'd think about the crud that washes into places it shouldn't be. Keep in mind that when it dissolves something and runs into a part, like the innards of a chain, that when it dries it leaves crap behind. Kinda like a muddy water line after flood waters recede.