80-grit sandpaper
g) Apply a thin, even coat of sealer or stain over a two- to three-board section with a paint roller with an extension handle or a sprayer. Two thin coats are better than one thick coat that does not properly adhere or dry. Do not allow the finish to puddle. To speed up the process, one person can apply the stain or sealer and another person can use a roller or broom to spread puddles and to work the finish into the wood, a process known as backrolling.