Actually, all of the above work to clean an atty. I use 91% isopropyl alcohol sometimes, water most of the time. Haven't bothered to invest in a ultra-sonic
device, and I'd probably drink the vodka not clean with it
Yes, 91% isopropyl alcohol can be used to clean a PV and contacts too, it's great stuff. It's my go-to cleaner for stubborn atty stuff. I always blow the atty out after using it and "warm" burn it. A very small amount left behind, if any is even present at all, won't hurt anything. It will evaporate away if you are patient enough (I'm not ... lol). If you do use it, check that the ingredient list is 91% isopropyl alcohol and water ONLY. Don't be stupid and use rubbing alcohol that has oils or other stuff in it. If you're worried about it at all, use the vodka, but vodka still may have some small amounts of sugars left in it. I suppose that the vodka is more idiot proof than the isopropyl alcohol, but more expensive too.