Scott,
I've just got in after doing 1200 sq.yds. of minging carpet tiles. I used the Charley Pads to agitate the solutions micro-splitter - much more effective than a brush.
As Ian has suggested, the shampoo tank is not used as the pads have internal sponges. Soak pad in water, wring out lightly and spin over the pre-sprayed carpet, either as a stand-alone bonnet clean, or as I did today, follow with a plain water rinse.