Vacuum slipcovers while still on furniture, and shake outdoors after removing. If washable, wash in warm water and laundry detergent. Wash one large slipcover and two small pieces at one time in average machine; do not crowd. Use soak cycle before wash cycle to remove extra soil. Use cold rinse at end and don't let them spin too much. Take out of washer while still quite wet, and either hang over clotheslines or put in dryer. Take out of while still a little damp.
Smooth over furniture and pull all seams and cording into place. Pinch pleats into sharp creases and smooth any ruffles. Open the window in good weather and/or use an electric fan near the window or furniture to speed drying. Or use a dehumidifier if windows are closed. Do not use furniture until slipcover is completely dry.