Jenolite
used to be very good, but has either changed for H&S reasons or has been overtaken by better products. Kurust isn't up to much either.
Fertan is VERY good and and I use a lot of it. The box section sills I put on my disco were externally treated with only fertan about 4 years ago and if it scratches off there is bright steel underneath. Not bad for something that should top coated within a year when used externally.
After that paint the repairs with Bonda primer or Bilt hamber electrox (amazing stuff - good as hot galv dipping) then top coat with either bilt hamber epoxy mastic and BH Dynax UB, or just Dynax UB as the underseat/topcoat and make sure to spray the cavities with BH Dynax s50. Don't put waxoyl near it for gods sake!
Buzz weld corroless coatings are also said to be very good, but I've had no experience of them as yet..
Bilt hamber products are very under rated and they're not well advertised for some reason, but are pretty much the best available in what ever they decide to make next. I'm not linked to them, but I wish I was... Maybe I'd get commission!