Very effective on all types of difficult and delicate surfaces. I use them primarily to clean metal surfaces before soldering, but I've also used them to give smooth plastic and metal surfaces some "tooth" before painting. Very efficient. Just keep the fiberglass threads away from skin, eyes, etc. and never inhale. I work with a fiberglass brush in one hand and a high quality vacuum cleaner head in the other to pick up bristles that break off by the thousands.