I've used a mixture of Dawn and Cascade dishwasher detergent with a splash of Super Clean and have gotten phenomenal results. A stiff brushing and then a power washing session will work wonders. I've also used a garden hose and did very well.
I'll use a stiff brush on a pole to get some extra power on the carpets. I hang them over sawhorses when I'm powerwashing them. You'd be amazed at the dirt and black water that comes rushing out.
Dry everything in the sun.
-Todd