Connect your garden hose to a high pressure power washer. Spray the deck and railings clean of dirt and grime to prepare the surface for priming. Allow the wood time to dry.
Place plastic or cloth drop cloths beneath the deck to protect the grass or concrete below it. When using a sprayer, paint can drift to other sections of your yard. It's essential to protect the area, especially if the deck is surrounded by plants or flowers.
Assemble the paint sprayer as per the manufacturer's specific guidelines. Fill the paint reserve with your exterior primer. Paint the railings first, followed by the floor surface and finish by priming any stairs that may be installed with the deck. Point the sprayer 6 to 8 inches away from the surface of the wood, applying the paint in even strokes.
Allow time for the deck to dry. Apply a second coat of primer. Inspect the deck for any drip marks, which can be sanded out lightly with the 120-grit sandpaper to give the deck an even finish.
Rinse the paint reservoir clean before adding your exterior paint. Reassemble the paint sprayer and begin applying the exterior colors in the same manner as the primer. Apply two coats of exterior paint and allow sufficient drying time between coats. In between coats, look for drip marks from the sprayer, which need to be sanded out.