How to Finish Fiberglass Doors

Remove any hardware from the door. You shouldn't need more than a Phillips head screwdriver to take off the knobs and strike plates.

Pour mineral spirits onto the door and wipe with a clean rag to remove any dirt or scuffing. Let the door dry completely and then wipe it with a tack cloth to remove any remaining small particles. Check the door for any imperfections. Occasionally a razor blade will be needed to remove persistent grime.

Use painter's tape to mask any glass on the door. It is best to cover the glass with paper that is cut to size and secured at the edges by the tape.

Apply an oil-based gel stain to the door with a brush. Brush the stain with the grain of the door for the best finish. A rag can also be used to apply the stain, by dipping the rag in the stain and spreading it evenly over the door. The brush method tends to be easier and creates a more even finish.

Coat the door with a protective clear top coat once the gel stain has completely dried. Because the fiberglass does not take the stain like wood, the clear coat is necessary to protect the door from scratching easily.