My first attempt with a rust converter has not gone too well. Tried it on my truck, first, just to see how it works. Bought the Rustoleum kind in an 8 oz. bottle -- brush on. It's white and water based. Some of the deep rust turned sort of black after quite a while, but nothing in the 15 minutes mentioned. It will rub off with a finger tip when applied over paint. Does temperature have an effect on this stuff? It was about 55 degrees or so. Since it was coming off easily, I sanded a bunch of it, and the red rust was still there under it. Should I try a different product, or did I just do a bad job of applying the stuff?