Pull all of your belt out of the door, and put a sheet over the bodywork to stop any crap flicking onto your paintwork.
I used AG Interior shampoo, A dish brush similar to below, A bucket of soapy water (car shampoo is what I used), Microfibres and a lot of elbow grease.
Spray the AG on to a section first, let it sink in, then scrub it hard, then get some suds from the bucket and scrub at it again. Keep rinsing the brush in the bucket and scrubbing the suds. Apply more AG if needed.
Work about 6inches at a time and wipe down with the MF cloth.
Leave to dry either out of the car, or fully extend them around the steering wheel/seats etc to let them dry properly before retracting them to the real to prevent rust.