2k urethane or epoxy primer?

Agree with what others are saying. Epoxy is a good foundation to build upon. Then lay your poly or urethane primer over that. If you miss the recoat window on epoxy (or anything for that matter) you scuff it before laying more over the top. Not a big deal. It's not uncommon to lay epoxy when the car will be sitting for along time while you work on other areas. I believe the stuff Summit sells is relabeled Sherwin Williams. Others sell relabeled Kirker.