Sand the grit from the door with 150-grit sandpaper. Use an orbital sander to remove the paint without cutting gouges in the door.
Dampen a cloth and wipe down the door to remove the dust.
Apply wood filler to the crack. Smooth the filler into the crack with a trowel until the crack is filled in. Smooth the wood filler over the door until it’s flush with the door. Sand over the wood filler until it’s smooth.
Paint the door with the oil-based exterior paint. Paint the door panels and the corners of the panels. Paint around the door panels. Allow the door to dry for six to eight hours.