Remove the door from the hinges and lay it flat on top of sawhorses.
Sand wooden entrance doors with a palm sander stocked with 180-grit sandpaper. Sand along with the wood grain. Stop sanding when the finish appears dull. Skip this step if the door is not wooden.
Sand wooden entrance doors with a palm sander stocked with 220-grit sandpaper. Sand along with the wood grain. Stop sanding when the finish feels smooth. Skip this step if the door is not wooden.
Abrade fiberglass doors to promote adhesion. Scour the door with 220-grit sandpaper until it feels slightly coarse.
Cover areas of the door you do not want refinished with painter's tape.
Coat wood and fiberglass doors with acrylic latex primer using a roller. Use a metal etching primer on metallic doors. Promote a flawless finish by smoothing the wet primer using a 3- to 4-inch latex paintbrush. Apply gentle pressure and brush in a long vertical motion. Wait three hours for the primer to dry.
Wash the painting tools with water.
Coat the primed entrance door with acrylic enamel using the roller. Use the clean 3- to 4-inch latex paintbrush to smooth the wet enamel. Wait two hours for the enamel to dry. Apply a second coat if you have poor coverage. Wait three hours before reinstalling the door.
Coat wooden doors with oil-based stain using a 3- to 4-inch oil paintbrush. Wipe excess stain from the door with clean cloth rags. Wait four hours for the stain to dry.
Wash the brush with mineral spirits.
Coat the stained door with varnish using the clean paintbrush. Wait three hours before reinstalling the door.