I have had good results with OxyClean spray, I just spray it on then hit it with the pressure washer.
Doto`s here I just steal some of the wifes carpet cleaner. Using a small pressure washer majes a big difference it lifts the dirt and gunk buried in the carpet.
I like Krud Kutter.It seems to knock the heck out of any stains I seem to get in my rig.From old coffee stains to fish blood & colored poweraid.Its enviro friendly & you wont break the bank buying it.I have 3 kids & with all the unfriendly colored snacks they & I bring on board it has knocked the snot out of them all! Might add my youngest had a couple frozen strawberries he snuck from the freezer about a week ago & thought mom was going to bust him with them in the livingroom.He decides to stick them under one of many of my wifes livingroom ornaments which sits on the carpet. Well she found them last night & lets just say they were no longer froze! The Krud Kutter did knock the stain out,with 3 applications luckily.Replacing $2000.00 carpet or buying $5.00 bottle Krud Kutter.Whew can you say GET-ER-DONE
For my carpet, I got one of those pressure washers from the Mens Mall, 1200 or 1500 psi, I hook it up to hot water, fan spray, tip the nose of the boat up start with the washer no soap, wash the carpet front to back, then take a good Craftsman shop vac, no filter, and suck every square inch of carpet, it is amazing how clean it is after and the water is nasty.