Drill brush attachments. Seen them used on MAD Detailing so I got a pack of about 20 on Amazon for $20.
Just starting to use them and they are great. The red one loosens dirt, pet hair, debris, etc. from carpet making it so much easier to vacuum up. Also straightens the nap for smooth even look when floor mats matted down the pile. Fits in tight places around seat belt anchors and seat frames.
The green one I'm using to remove stains. Spray on a cleaner and let the brush do it's thing. 10 times faster and more effective than a hand brush.