I have done a search and read the prior posts. I have sandblasted the bottom of my 64 cab and I am ready to undercoat it. I want to use spray cans for application and plan on using 3m underseal undercoating since it seems to be hightly recommended by people on this site. The question is, should I prime coat the metal then spray over it with undercoating or should I spray the undercoating directly on the bare metal? If the answer is prime coat, any suggestions on a good type to purchase (in a rattle can) Thanks in advance for any input, Scott