I'm in the process of painting some old metal kitchen cabinets. I've washed the cabinets thoroughly, scuffed them using 0000 grade steel wool, tacked clothed them, and painted using rustoleum oil-based paint. However, when they dry, there are small 'bumps' or 'dots' in numerous places on the newly painted surface. I've sanded these down and applied a second coat and they still reappear (not necessarily in the same places). They don't appear to be dust. Any help is greatly appreciated.