Purchase a gentle laundry detergent. It should not contain bleach or harsh cleaning chemicals. A natural detergent is the best option for cleaning a comforter. If you know the type of fabric your comforter is made of, check the detergent label to make sure it's safe for that fabric.
Fill your bathtub or a large sink with warm water. Add about a half a capful of the laundry detergent.
Place the comforter in the soapy water to wash it by hand. Use a cloth to scrub any areas that are soiled. Allow it to soak in the water, turning every few minutes, for about 10 minutes.
Allow the water out of the tub and rinse the comforter thoroughly. You can use the water from the faucet and buckets of water to rinse.
Squeeze out some of the water gently. Hang the comforter to dry. Drape it so that no one side gets all the weight. Draping over an area like a table or piece of exercise equipment can work well.
Add comforter clips to each side of the comforter once it's completely dry. These clips helps prevent the comforter from shifting once you make your bed.