I have gotten the white/green scrubber pads from directmopsales.com and some of their blue scrubber pads and have used them on every type of carpet and they work great, I use them on stained and spotted areas, and it does not hurt the carpet fibers, then I use the cloth pads to clean up the dirt, in which I have cut down on the amount of cloth pads I use, because of this.
The best thing about these pads their inexpensive.....
On my toughest commercial jobs, I have first run either my Cimex or my Orbitec CX-20 using FiberMax pads, to break up as much of the tough soil as possible. Then I have gone back over the area with either a Challenger or the Orbitec with absorbent cotton or mostly cotton pads. I'm not sure you can do much more.