So couple ways you can do it, you can fill, spot prime and then go over the full thing
So you want 320 or 400 grit.
Key the damaged area, then add the dolphin. It’s self leveling.
Once cured use a block and 320/400 so you don’t dig in. Once all your chips are done.
Flat/scuff the whole grinder, then clean and spot primer over the dolphin. Once cured flat the primer and paint.