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