I have a couple rusty cars that I cannot get inside for the near future. I would like to stop the rusting on the roof and other top surfaces and find what to coat them with for protection. The cars are 67 Ford Fairlanes and are complete so there is chrome that is a consideration to not damage. I have heard that phosphoric acid would be what I need to use. Is that a good product to use? And what to put on then? I would like to use something I can use with a brush so I get a good coating, so not just using spray cans. Would regular rustoleum be a good product? Thanks for any ideas.