IF you're talking about the spray-gun (Suds-O-Gun) attac
Well, I tried it ONCE....but, honestly, it took FOREVER to dry...and then of course, if you use the one of the straight suction tools (the upholstery tool, for example), it doesn't raise the knap very well. I ended up using a Kirby Vacuette for some brush roll action.
Of, course I just sprayed the suds right on the carpet. MAYBE if you did it something like spray the suds into a bucket, or on newspaper (as shown in one of my Kirby manuals), and then just spread what you need from that using a damp sponge, it might dry better/quicker. That MIGHT work.
Good luck.