If you don’t want to use chemicals and you also want to remove the paint along with the rust, use a power tool like a grinder ...

And we dip it in the water-based rust inhibitor to stop further rusting until you're ready to paint. I think chemical dipping is the most thorough way to remove all paint and rust from a car body.

Gently scrape away flaking paint with a two-inch plastic putty knife. If all you have is a metal putty knife, go ahead and use it, but go easy to avoid making new scratches. Sand lightly with 150-grit ...