To create a perfect polyurethane finish, sand the surface with an orbit sander, apply sanding sealer, sand the surface again, apply a thin coat of polyurethane, and let the coat dry. Gently sand the surface with a sanding block, remove bumps, and wet-sand the surface with fine-grit sandpaper.
- Sand the surface
Sand a hardwood surface with 320-grit sandpaper and a soft wood surface with a 220-grit using a random orbit sander. Apply moderate pressure when sanding to avoid gouging the surface. Sand until all the dents, knots, holes, scratches and dings disappear. Wipe off the dust generated from sanding with a tack cloth.
- Apply sanding sealer
Apply thin shellac to the sanded surface, and allow it to dry. Set the orbit sander on the lowest mode, sand the surface again with 320-grit or 220-grit sandpaper, and repeat the process.
- Apply polyurethane
Using a soft, bristled paintbrush, apply a thin layer of polyurethane to the surface, allow the first layer to dry, and then sand the surface with a sanding block. Rub away any bumps with steel wool, and dust the surface with a tack cloth. Repeat the process until the surface becomes smooth, and wet-sand the surface with 2000-grit sandpaper.