Remove the door from the hinges and lay it on a flat surface.
Sand the surface of the door using a sanding buffer with a medium-grit sanding ring. This will remove any paint, roughness or debris from the door's surface.
Wipe the door using a washcloth to remove any dust and debris caused by the sanding.
Spread a 1-inch-thick layer of medium stucco grout over the entire surface of the door using a triangular trowel. Apply the grout in a choppy yet even layer, stopping 1/2 inch short around all of the edges of the door. Allow the grout to air dry for 12 to 18 hours.
Paint the stucco-covered door with clear waterproof sealant using a 2-inch round paintbrush. Allow the sealant to dry for 12 to 18 hours before hanging the stucco-covered door back onto its hinges.