I've rarely cleaned curtains, but when I did, I thoroughly vacuumed, then sprayed with a fine mist m/s and quickly extracted.
On one occasion, I oversprayed onto a wall and caused a run on the recently painted wall, fortunately the client was so impressed by the cleaning, she excused the error.....others might be less charitable.
Ironically, I have never used the Ninja's built in Dry Solvent facility !
rob m
ps
strong possibility of shrinkage if you wet the lining