I haven't tried it with overspray, but all I get is shine. Wax on, wax off, as it were. What kind of outcome are you getting?

My experience is that you have to do a relatively small area or a larger area 2-4 times, depending on the paint. But it does get done. Of course, scratches all the way to the metal can't be repaired. I have some thoroughly battered raleigh fenders. The paint is /really/ bad, practically a matte finish, with deep scratches and some bare, rusty spots. Several applications of scratch-x later, I've restored about a third of one fender. I can examine my individual teeth in the mirrory finish.