I have new panels that have black EDP coating and others that are just raw steel. I asked this forum if I should shoot 2-part urethane over the EDP because that would be the same primer I would use on the raw steel (after etch-primer). The consensus was that it would be a good idea to scuff the EDP and spray 2-part urethane in order to make sure that paint was applied to the same base. It also allows you to block-sand the panels to make sure they are perfectly straight.