recommended primers for painting metal (with oil top coat)?

I'll be HVLP spraying some toolboxes in the near future and wanted some opinions from those with experience on what primers work well on clean metal. (Preferably sandable and can fill scratches.) The top coat will be an alkyd/oil tractor enamel.

Happy to use a Rustoleum product if that works well, or don't mind spending more for something noticeably better.

I'd start with a two part epoxy primer, like PPG Omni MP170. Then to fill in the scratches, maybe some high build primer.

With the use and exposure to chemicals that a toolbox sees, anything that doesn't use an activator or hardener isn't worth the time it takes to mix.

PPG epoxy...that really is cooking with grease. I'll look into it, thanks.

Regarding activators, I couldn't agree more. Before I knew about hardeners I once painted a toolbox with Rustoleum red and it scratched really easily.