I'm trying to figure out what part of the car you want to cover. It would have to be a flat surface or it would be full of wrinkles. You would have to also have a surface that Ultracote adhesive would stick to. Ultracote and Monokote have both been used for decking on racing model sailboats. Secondly, why not use Bondo or some regular body repair material if it's a full sized auto. If it's a model ?