While you're at it, sand all the other areas you treated for rust to smooth them out and prepare them for painting. Any spots you've sanded down to the bare metal must be primed before you paint ...

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, sander, oscillating tool or drill to remove rust from metal tools.

So if there's aluminum, magnesium, or a pot metal on the car ... chemical dipping is the most thorough way to remove all paint and rust from a car body. It gets to places that physical medias ...