Scrape the paint away from the doorknob screws with a paint scraper. There may be several layers of gummy paint, so use two hands close to the end of the scraper blade and slowly peel the layers off the screw heads. Cut around the outer edge of the hardware with a utility knife to break the paint seal between the hardware and wooden door. Remove the screws with a screwdriver and take off the doorknob and back plate.
Fill an old saucepan or crockpot with 4 to 5 inches of water. Sprinkle in enough baking soda or laundry detergent to cover the bottom. Place the door hardware in the pot and let simmer for two hours. The heated baking soda or detergent will act as a paint remover in time.
Check the hardware every two hours to see if the paint is peeling away from the surfaces. Leave the pot simmering for as long as it takes to loosen the paint. It may take up to eight hours to remove paint.
Remove the hardware with tongs and lay it on an old towel to cool. The metal will be too hot to touch for several minutes.
Put on rubber gloves and scrub the surfaces of the door hardware with a nylon scrubber as a final paint removal process for the stuck-on paint chips. Restore the luster of brass with brass polish and put the hardware back on the door.