I like Ospho if I can't media blast down to white metal. After 24 hours, I wet down a rag with Ospho to wipe off the white residue left from the chemical reaction. I then wipe it down with acetone (you could use wax/grease remover), before epoxy primer.
Carl


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission