Prepping metal for paint...eventually

[General23cmp]

I’m repairing body panels on my own for a professional to paint later. What can I put on the metal that I can do in my small shop, that would make it ready for the painter later? I don’t want it to rust after getting it right, but I also don’t want him to have to remove whatever I spray on it unless unavoidable. I’d expect rattlecan primer from the dollar store to be unadvised, for example. Thanks.