I want to treat some pitting on the roof caused by rust under the vinyl top so it won't be an issue later on after I put a new top on it. I haven't tried the products from POR-15 personally but if I understand it correctly the stuff sets up extremely hard and it has to be brushed on. I want to be able to sand the roof smooth and topcoat it before installing the new top and it sounds like this product would be difficult at best to sand. I've tried Extend by Permatex and wasn't impressed. Any recommendations on any other products to kill rust but still be workable?