Fill a large pot with 1 gal. of cold water and 1/2 tsp. of laundry detergent.
Put on rubber gloves to keep your hands from getting wet and dirty.
Place the old hinges and doorknobs in the pot of water. If any of the old doorknobs contain glass or ceramic elements, set those doorknobs to the side; do not place them in the water. Do not overfill the pot--you don't want the pot to run over once the water starts boiling.
Place the pot on the stove. Turn the burner on low heat.
Let the pot boil for 30 minutes. Check the water level in the pot and add water if needed. Let the pot boil for an additional 30 minutes.
For the glass or ceramic doorknobs, dip just the metal portion of the doorknobs into the pot of boiling water for 15 minutes. Do not submerge the glass or ceramic element into the boiling water--the hot water may damage the glass or ceramic.
Remove the pot from the stove. Let the water cool for 15 minutes.
Lay a clean rag or shop towel on a flat surface.
Remove each of the old hinges and doorknobs from the pot and place them on the clean rag or shop towel.
Scrape the softened paint from the metal with a plastic scraper. Use force as needed to remove any stubborn paint spots.
Wet a clean rag or shop towel with warm water and wipe each old hinge and doorknob.
Apply a teaspoon of metal polish to a clean rag or towel.
Polish the old hinges and doorknobs with the metal polish-soaked rag or towel to keep the hinges and doorknobs from rusting and tarnishing.