What is the process for cleaning upholstery and carpets?

1. Vacuum the carpet or upholstery to remove any particles of dust or debris. 
2. Use a spray bottle containing a mixture of water and upholstery cleaner, and spray this mixture on the carpet. 
3. Use a drill bit brush to agitate the pile.
4. Use clean water from the extractor to remove the dirt. You won't believe your eyes when you see the dirt being sucked away.

This is one of the best practices that has emerged from mobile auto detailers over the past ten years. You can find many videos of professional detailers demonstrating this on YouTube.