Steve, if they are Kato's, whatever you do, don't use brake fluid! Kato uses a different type of styrene from most manufacturers. The brake fluid will cause the styrene to become brittle and crack!
Ask me how I know....
What I would suggest you try is a bottle of Scalecoat's Wash Away. Its made for stripping plastic, is reusable, and is a very good stripper. I've used it to remove the old formula paint off of old Kato bodies that nothing else would touch. That paint is tougher than the paint on the newer Kato bodies.