Marx 6-inch cars in beat-up condition are cheap and easy to find, but you can dramatically improve their appearance by repainting their frames. If the body is scratched up it still won’t be a showroom car, but you can halve the number of scratches on it and it will look nicer. Here’s how you go about restoring Marx 6-inch frames.
Whatever paint Marx used responds well to a soak in purple cleaner, or even plain ammonia, if you can stand the fumes. Pour enough into a plastic container to cover the frame, then dunk it. Within a couple of hours the paint will be bubbling off.
Rinse the frame thoroughly after soaking and let it dry. Then spray it with some primer and let it dry for at least 24 hours or better yet, four days.
You can spray it with a topcoat as well. Satin will match the original finish most closely and allow you to pick up the detail that Marx pressed into the metal. Gloss is a little bit too shiny. If you like the early red-frame cars, you can even try painting them red instead of black and see how you like the results. Spray outside and elevate it enough that you can spray at it while standing. Spraying at it hunched down is more likely to give you paint runs. You’ll need to practice your technique a bit because paints vary, but after a few cars you should be able to get nice results.
Let it dry at least 24 hours before reassembly. If you have the patience, wait a week. If the paint still feels the least bit tacky, it’s not dry and will scratch easily during reassembly. Once the paint is thoroughly dry, the finish is likely to be more durable than the original.