Washing the deck consists of scrubbing the deck with a cleaning solution and a stiff bristle brush. You will need a bucket, a brush with an extension pole unless you want to be on your hands and knees, cleaner and a garden nose with a water nozzel.
First, spritz the deck with water to soften the dried cellulose fibers. This 'pre-rinse' will also allow for the cleaning solution to be more easily dispersed throughout the deck. Mix your cleaning solution in a 5 gallon bucket with water following the instructions on the container. Next you can begin to scrub the deck with the grain using your stiff bristle brush to remove dirt, mildew, mold, stains etc. HINT: If the deck surface is large, mix and divide multiple batches of cleaning solution. The concentration of the cleaning solution should remain consistent throughout the project.
You can then use your garden hose or a pressure washer to rinse the surface of the deck. Try to time your deck cleaning project for nice weather. It is best if you can allow your deck to dry for 24-48 hours before staining and sealing.