Dampen a rag with mineral spirits. Rub all of the door surfaces thoroughly to remove any remaining bits of paint.
Use fine-grade steel wool dipped in more mineral spirits to scrub off stubborn patches of paint that may linger after stripping. Examine nooks and crannies for such residue.
Sand the door with a series of progressively finer-grit sandpapers. Begin with a coarse-grit paper, such as 120, and finish with a very fine-grit, such as 220.
Wipe the entire door thoroughly with a tack cloth to remove the sanding residue. A tack cloth is a special cloth that has a manufactured sticky surface meant to adhere to the small particles that sanding leaves behind. Your clean door is now ready to be refinished as you desire.