I am not Spray Tech, but I do have an answer for question #3. I just finished painting my Dodge Challenger using DuPont 615 VariPrime as my base. When I block sanded, I used a very light dusting of good ol' 80S red oxide lacquer primer for my guide coat, with perfect results. I think SEM makes a guide coat specific primer if you are still concerned, but I know even House of Kolor systems use lacquer guide coats over their epoxy primers. Good luck. Brian