Stains are tinted sealers for wood. They protect wood from harmful UV rays--the darker the stain, the better the protection. The type of stain expresses its darkness: clear sealer, semi-transparent, semi-solid and solid. Solid stain may hide the natural grain of the wood; semi-transparent or semi-solid will allow it to show through. Some stains have performance-enhancing additives. For example, a stain containing mildewcide and fungicide slows the growth of mold and mildew. Using a spray gun to apply stain works best using a water-based stain on a large area. The application method is the same whether staining a deck or fence.
Fill the reservoir of the paint gun. Plug the paint gun's power cord into an extension cord that is properly rated for the paint gun.
Hold the spray gun a consistent distance from the surface of the project to apply stain. Work at a continual speed and work from top to bottom. Use a back-and-forth motion across a section that is a width of your choosing. The width of the spray gun's spray pattern will determine your stroke. For example, if the width of the spray gun's pattern is 12 inches, you will spray across a portion of the section, then move down approximately 11 1/2 inches to make the next stroke.
Brush the stain on the boards with a paintbrush to ensure the stain is worked well into the surface and any crevices, such as between boards.
Clean the paint gun carefully according to the manufacturer's directions to help ensure future usability.