Wait three-to-five sunny days after the pressure washing is complete before beginning your project. Pressure washers exert strong force and cause water to deeply penetrate the wood. You must allow ample time to be sure your deck is completely dry before the sealing process.
Sand your deck using a high-grade sand paper to eliminate any rough edges that may have previously existed or may have surfaced as a result of the pressure washing process. Only a light sanding is needed. Sanding the wood will also allow the sealant to penetrate the wood deeper and will lead to a most durable final product.
Apply the sealant using either a paint brush or a roller. Using a roller on the flooring of the deck will save you lots of time and will allow the chemicals to penetrate the wood deeper than with a single brush. Use a brush for the railings and any parts of the deck that contain small crevices. Apply a thin, even coat to all areas of the deck. Be thorough and ensure that you are not missing any spots as you work.