The best way to attack curtain cleaning is to take a sunny day and do them all at once.I like to take them all down and throw them in the washer on delicate. While they are washing, I use that time to clean the windows.
Most curtain fabric will hold up in the washer if you use the delicate cycle, but if you are talking about drapes, you may need to purchase a commercial cleaner which you can spray on and then vacuum off using the attachments.
Do not try to force drapes into the washer unless you take the time to remove each metal hanger individually and have a new washer which can stand the load capacity. When in doubt, the homemade dry cleaning method is best to freshen heavy drapery material.