I use the drimaster tool on curtains, acceptable results every time,
the method I use personaly is to thouroughly prevac, mist with m/s aggitate with m/f cloth then simply extract with tool.
what I do find to be effective is place terry towel over hand tool and simply run down the curtains ,adjusting the toweling as dirt is transfered on to towel.
A good tip told to be my JK was to hold behind the curtain a plastic builders float " thanks John, very effective" .
this method prevents over wetting although the flow willl be continuos because you are using the drymaster, and adjusting the main water flow control on the tool will help.
curtains do seem to find their own originol form when cleaned whilst hanging but they can be simply dressed by using this method.
The last curtains I cleaned for a custy would never take to cleaners , the last time she did they shrank them 4 inches, so not happy even as routine the cleaners insisted on her signing a disclaimer before cleaning she did not expect that!!!.
most curtains will be prone to a minimal amount of shrinkage, and their is I believe an acceptable loss% standard somewhere, not sure what it is , but somebody may enlighten us

Geoff