Hi Dan,
I use my dry cleaning machine for curtains at least once a week, it brings in a lot of work where people want the curtains done the same time as carpets or upholstery, the best spotter I've found is chemspec heavy duty soil lifter(but used undiluted). the only time I will use a water based spotter is when I've blocked the material first, otherwise you will get water marking.
All the best
John