Have you got a handi groomer or similar?
www.prochem.co.uk/IMAGES/accessories/PC4201.jpgA stiff brush will do a similar job but the handi groomer is much better.
Use it in conjunction with the vacuum to flick up the dust out of the base of the pile. It's easier on polyprops as you sometimes need to be a little vigorous, which obviously some wool carpets don't like.
Try a moderate pre spray of whatever you use but mix it weak, you're not relying on chemistry too much at this stage. Agitate it a little, within what the carpet can stand, then give it a good thorough rinse through. Heat is almost irrelevant too, back the heat off to save unnecessary risk from damage.
You might still be left with an orange hue, even though the worst is gone. Try an alcohol based spotter on a towel, blot and inspect, it should show a decent colour transfer. Depending on the size of the area affected, either blot it over or carefully spray from a trigger sprayer and agitate in again. You should get almost instant results from extraction.
Sometimes there's still a teeny weeny orange hue visible on very light carpets, but it normally looks better after drying. If this is the case, dry it off
before you show the customer, then ask them what they think.
In case you were wondering, Sky have a national account with ServiceMaster, we clear up lots of messes where they've drilled the cables through the walls :
