AddictedtoBling --
Yes, I premix in a 32oz spray bottle, Meguiars APC+ at 10:1 and spray the carpet, dont spray too much except maybe a little more on stains, let it sit for a minute, and brush it carefully.
Then my Mytee HP60 Extractor comes in and rinses and extracts out tons of dirt - no matter how clean the carpets are initially.
My Recovery tank will always be full of dark brown water, and undissolved dirt, sand, etc.. when I empty it.
Sometimes I will use a Steamer through a towel to really heat up the sprayed APC, scrub, extract, and they look like new. The smell of APC is neutral, no residual soap, Clients love it.
Your way works too, but the way I do it may be a little quicker, and I can target the worse areas with the spray and lightly hit the areas that are relatively clean already. The Extractor is the great equalizer though because it hits the entire area with hot water and removes all the loosened dirt, gunk, completely from the carpets.
For really dirty carpeted floor mats that have like a lot of grease, sand, etc., sometimes its faster to clean with soap, and rinse with a pressure washer, and then Extract all the water, and hang them up.
Another way to help pre-clean just the embedded dirt, would be to blow high pressure air on the carpets before anything to help loosen and remove alot of the dirt. Just be careful where you do this, and watch out you dont blow the dirt in your eyes.
Dan F