The Express' finish is garbage. It is doubtful that you have gotten off all the rust since it rusted the first time so it pops back up quickly. I would get it professionally parkerized. Cheaper alternative would be Duracoat or similar but you must make sure there are no traced of rust before you paint.
"Suppose you were an idiot, and suppose you were a member of Congress, but I repeat myself." Mark Twain