As usual, good advice from sstock.

Some advice, perhaps unneeded:
- clean/wash the metal (to bare and oil free)
- spray on the epoxy primer
- sand as suggested by product sheet
- then, use a compatible filler
- sand as suggested by product sheet
- then use a compatible primer surfacer
- sand as suggested by product sheet
- wipe clean with suggested solvent, twice
- final-coat spray
- color "sand"/polish within the "window" suggested by the product sheet (the longer you wait, the harder it gets)

Listen to the pros, if they post corrections to any of the above.