Pour 1/4 cup trisodium phosphate into a bucket containing 1 gallon of water. Dip a scrub brush in the mixture and shake it off. Scrub down the chair. Allow it to air dry.
Fasten a piece of 100-grit sandpaper to the bottom of an electric sander. Run the sander across the surface of the chair. Repeat with 220-grit sandpaper.
Run a vacuum cleaner across the surface of the table to remove all the dust from sanding. Repeat with a tack cloth.
Submerge a 3-inch nylon paintbrush in oil-based paint. Cover the chair with a light coat of paint. Allow it to dry overnight. Repeat with a second coat of paint, giving it the same amount of drying time.
Cover the chair with a light coat of clear polyurethane to protect the paint. Allow the polyurethane to dry the amount of time the manufacturer recommends.