Before applying TotalBoat White Knight Fiberglass Stain Remover, wet the area. Always test in a small, inconspicuous spot before attempting a larger area. Using a brush or rag, apply a thin layer of White Knight to the surface and allow it to work for 10 to 15 minutes. Then, scrub with a soft brush or sponge. Thoroughly rinse the surface with water to remove White Knight before it dries. Some tough stains may require a second application.