Use the delicate cycle, and wash the garment in the washing machine. Remove it from the machine as soon as the wash cycle is finished.
Fill the iron with water and set it to its lowest or coolest setting. If your iron has a chiffon setting, adjust it to that.
Place the garment on the ironing board, taking care to shape it properly. Cover it with a damp towel to help it stay moist throughout the ironing process. Expose only the section you are ironing.
Iron the garment one small section at a time. Cover the section being ironed with a thin, damp towel to prevent the iron coming in direct contact with the chiffon. Work from the center of each section out toward the edges, and lift the iron periodically to check your progress.
Continue ironing the garment one section at a time until the entire piece is wrinkle-free.