How to Stain and Seal Hardwood Floors
Sand lightly and apply the second coat of polyurethane.
You’ll need to rough up the smooth hard surface from the first coat of varnish so that the second coat will adhere well. Sand lightly with a fine sandpaper, like #220. Use a tack cloth to wipe up all dust. Apply a second coat of polyurethane, and allow to dry at least overnight.