After power washing your deck you may notice that the wood fibers are raised creating a layer of fuzz on top of the decking.  These raised fibers can lead to splinters as they dry out.  You can easily sand down the surface using a 5" orbital sander or a sanding sponge.  You will want to sand with the wood grain and use the proper grit sanding paper.  Use 60-150 grit sanding paper or discs will work best.  Courser sanding paper could damage the wood further and finer sanding paper will take too long.  Make sure the deck is clean and dry before sanding.