Featherfill G2 is what I use. Evercoat makes it in few colors, I use grey for lighter color cars and black for dark,I also mix them to get closer match, black seems to sand easier due to higher zinc content,but any of them provide great results.Buff color seems to dry too fast though if you are trying to shoot the whole car. Before the G2 I was using Featherfill until they came out with G2. You can never go wrong with any Evercoat product.I wouldn't use anything else especially at $50 a gal.However, do not apply it directly to metal.