I agree with Deve.

- Blast to clean metal and assess damage (and maybe find previous bondo/filler/poor-repairs that have to be removed).

- epoxy prime

- clean (remove primer) from areas that need metal replaced/repaired

- repair/replace metal

- prep part for priming (whole part or worked-on areas)

- epoxy prime (whole part or worked-on areas)

- prep/fill/seal/etc for painting