Mix 1/3 cup trisodium phosphate and 1 gallon water in a bucket. Submerge a scrub brush in the mixture and scrub the door. Allow it to air dry.
Cover the door with a thick coat of paint stripper using an old paintbrush. Allow it to penetrate for five minutes or as designated on the package. As the paint stripper is penetrating, sharpen the tip of your metal paint scraper with a metal file.
Scrape off the old finish with your metal paint scraper. When finished, attach a piece of 80-grit sandpaper to the bottom of your electric sander.
Run the sander over the surface area of the door, removing the remaining finish. Repeat with 200-grit sandpaper and 300-grit sandpaper to bring the wood to a silky finish.
Wipe down the oak with a tack cloth, wiping off all the dust from sanding.