I haven't used my shampoo brush in 15 years.
That was when I discovered that a pre-spray saturated scrub bonnet works better in every situation.
Unless we're bonnet cleaning or bonnetcRapping*, we use the same pre-sprays we normally use.
We just roto scrub them and extract as normal.
*BonnetcRapping is a term I use for when we use Pixie Dust encRap juice and stretch a bonnet a country M-I-L-E before we change to a clean bonnet.
Here's what I'd suggest Bryan, get a pad driver for your new rotary.
(you'll need one regardless)
Borrow a shampoo brush from someone before you buy one, then do some side by side evaluations on a mod to heavy soiled com carpet.
Compare a shampoo brush, a pre-spray saturated synthetic green striped scrub bonnet and a white or biege VCT pad.
Compare the side by side results.
You'll be WAY ahead of the game, cause you won't have to take anyone's word for it.
..L.T.A.