I haven't used the Polly Scale product but have have tried the Testors product. And I don't particularly care for it. It just doesn't look right to me. If you think about it, black rubber tires tend to grey as they get older. In my opinion, the Testors is too brown. For years I used a Pactra product call Hot Rod Primer - It was a dark gray about midway between flat black and panzer grey and looked great. Still have a bottle I use a little of on occasion.