Buy some Capture at Home Depot. Use the Capture pre-spray for the bad places. Rent a floor buffer. Sprinkle the Capture on the carpet. Use the buffer to rub in the Capture (if it's just a small area, I do it on my knees with a small brush and no buffer). Wait according to the package directions (at least 30 minutes unless you overloaded with pre-spray).
My husband developed Capture back in the late 70's. Oreck calls it something else, but it is hubby's Capture.
Even those carpet cleaning companies who say they are using a "dry" product are not using a really dry process. It's like washing clothes and not being able to rinse them. The cleaning residue is still there, and it actually attracts more dirt.
BTW my husband is no longer with that company and thus receives no honorarium for this product. But it is still a great product. One would never use anything else if they understood the chemistry of it all.