Check out Evapo Rust. It's an all natural, biodegradable rust remover that more or less bonds strictly to the rust particles and removes them, leaving the rest of the item in place, that way you don't "scrub" away something vintage you may want to keep on a piece. A 1 gallon supply is about $20 (give or take) and can be found at a lot of auto parts stores. They even have directions available for making a diluted spray specifically for use on body panels.