Personally, I'd be more afraid to use any product that claims to "dissolve" contaminants than using a clay bar. If it can dissolve metal particles and the like, what else is it possibly dissolving? I'm not knocking ABC, I know others have used it with success, but it's my opinion that claying is safer and easier than chemically treating your paint, which may not be 100% effective.
Claying is very simple, there are two basic rules to keep anyone trouble free: 1. Use plenty of lube, never use clay on a dry surface and 2. Always work with clean clay, either by tearing off pieces or folding/kneading. That's it, very simple IMHO.