Product review (2 stars): Not worth the cost and effort
It doesn't work. I carefully cleaned and sanded all the rusty spots to bare metal using a dremel. I wiped everything down in acetone to ensure the metal was perfectly clean and then applied several layers of this gunk. A few months later there are rust spots peeking through. Not on every single repair, but a good many of them. On closer examination of the failed repairs it seems that this product allows bubbles to form during application, these voids in the coating allow water to get at the metal underneath. I think I'll try some polyurethane next.