I don't believe in any of those "rust converters"

To remove the rust you need to hit it with a wire wheel on a grinder, or a similar rust removing wheel - whether it be a flapper wheel or disc or one of those fibre discs that look like a giant gasket remover.

Good old fish oil is a good next step. Its highly penetrative, very corrosion resistant and dries to a film you can paint over.

I like to use a kill rust type initial primer over areas that had rust, just make sure its sprayable. Then seal that with a normal automotive primer.