I painted the exterior of my square body last year and the jambs but the wife noticed the lower door panels and lower dash etc of the interior isn't going to match old vs new color wise. I'm using Metalux which worked fine over the gray epoxy and then reduced black epoxy as a sealer. My question is can i scuff these parts inside with 600 grit and just shoot them with my base and universal clear? Or will i need to epoxy everything just for adhesion purposes? I'd like to avoid that step if possible since its not a show piece inside just a driver/resto deal.