hHow clean is clean? I have scraped it with a a scraper, wire brushed the residue left sticking to the joint. There is still a thin layer of sticky black residue left from the wire brushing on parts....
I use denatured alcohol and can be bought in one gallon cans at Home Depot, Lowes, or any hardware store. It cleans good, evaporates quickly, and is a mild enough solvent that it does not harm paint surfaces.