Mix 1 tablespoon of dishwashing detergent in a 5-gallon bucket of warm water. Place indoor furniture (except large pieces, such as bed frames) outdoors on a sturdy surface.
Remove fabric cushions from the furniture (if applicable). Wet a sponge in the bucket, and scrub the furniture. Use a nylon scrubber to remove stuck-on spills such as food or bird droppings.
If your furniture has dirt stuck in crevices, use a toothbrush or small bottle brush to clean these areas. Wet the brush down with warm water. Add a drop of detergent, and scrub until it is clean. You may need to rinse the brush if it gets too dirty. If so, simply reapply detergent and scrub some more.
Rinse the furniture by spraying it down with a garden hose. Dry the wrought iron immediately with towels to prevent rust. Make sure you dry all crevices and creases as well.
If you do find rusted areas as you clean your furniture, finish cleaning it, then scrub the rust with fine-grit sand paper and rinse the piece thoroughly. Wipe the area down with a cloth to remove remaining rust particles. Use a touch-up paint intended for wrought iron -- you can find these paints at most home improvement stores. Let the paint dry fully before using the furniture.