I am a retired engineer, hobbyist and hopeless gear head. I am restoring a 1971 Charger Supper Bee. I purchased your SEM Pro-Tex truckbed liner system for the first time. I am planning to use this system as an undercoating. I have removed all old undercoating and sand blasted the under side of the Bee to bare metal. When I received the SEM product the instructions stated I should apply a 2K epoxy or urethane primer over bare metal. What would you recommend for this primer?