We bought a front door that was primed ready to paint. It is a Masonite Craftsmen Style door with a smooth finish and a dentil shelf. The guy at Home Depot told us to buy an exterior paint to use on the door. We bought Behr exterior finish paint in Ruby Ring which is a red color. We painted 2 or 3 coats with plenty of time to dry in between coats and would hand sand it. It still was not getting smooth. Finally we used a sander, but big flakes was chipping right off. I started examining further, and along the shelf I can leave an imprint of my fingernail in the paint that was painted over a month ago. We're in the process of building. We decided to put the door aside and deal with it later, but the later is coming up fast.... So is there is a hardener for paint? Any suggestions? My husband does construction for a living but has never dealt with a paint issue like what we have with this door. How do we get this issue right? I do have the smooth rollers for doors and cabinets for what's that worth on the main parts of the doors. I know that doesn't matter on all the detailed portions though. Anyways... I see beautiful red doors all the time, so why are we having such an issue with getting a nice smooth finish?