There is a lot of actual engine paints for the automotive builders(full scale) ,that he can use ,main thing is, to not pile, the finish on it ,and yes the gloss finishes, basically ,wipe clean with a rag..Flat colors will hold the, grunge, and grime, for sure.A more pourus texture to it(flat)..I`m sure he`s got ,some good options, to think over now, though..D.B.