I use a pail of soapy water with a brush, scrub it with the brush a little and use a shop vac to suck up most of the water. It works well.

 

Tuff Stuff spray foam upholstery cleaner , about $2.50 and works really well,spray entire area and let soak for 30 secs,then w/ mild brush scrub both vertically and horizontally,light spray again and then wipe with clean terry towel,let dry,for stubborn stains spray and let soak for 10 mins and repeat