Put on rubber chemical-resistant gloves and eye protection. Pour a small amount of the liquid sander deglosser into a metal or chemical-resistant plastic container.
Brush a coat of liquid sander deglosser onto the surface of the wood you want to reseal with a disposable paint brush. Allow the sander to set for five minutes to break down the gloss. Wipe the surface with a clean cloth to remove the top layer of finish.
Allow the wood to sit for two hours and come back to it. Wipe the surface again to remove the remaining gloss and chemical sander.
Wipe the surface with odorless mineral spirits on a clean rag to remove sander residue that might damage the new finish or cause it to fail. Sand the project lightly with emery cloth and wipe the resulting dust from the surface with the tack cloth to complete the preparations.
Shake a can of water-based clear finish in your chosen color and sheen for at least a minute to thoroughly mix it. Allow the finish to sit for fifteen minutes so any bubbles in it burst. Open the can.
Apply the finish to the surface with a soft-bristle, medium-width brush, working around the outside edges and in hard-to-reach places first. Work with the grain as much as possible.
Apply finish to the rest of the surface to seal it. Work in long, straight, overlapping strokes with the wood's grain. Spread the finish as smooth as possible to prevent runs and drips in the surface. Allow this coat to dry to the touch.
Rinse the brush in odorless mineral spirits and then in soapy water. Blot the brush dry with paper towels. Apply a second coat of finish in the same way using the dry brush. Allow the finish to cure completely before returning the piece to normal use.