Sanding the handrail of your deck is very important and is where people gage the smoothness of your sanding job. Make sure to sand the top, edges and bottom of the top handrail because all edges are touched and will be prone to splintering if not sanded. Again, use 80 to 100 grit sandpaper for the handrail but try not to go higher than that or you may limit the absorption of the stain or sealer in to the wood.