Don't overthink it. I de-grease and wire wheel everything to the best of my ability and then clean it with soap and high pressure water.

Then I rattle can it with Rust-O-Leum or Bill Hirsch. It pretty much lasts forever.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)