Richard has the answer. That spotter would be fine for one chair, but if you have the whole living room suite to do or an office full of chairs, you will be worn out with bucket brigade and time for the water to get hot.
U.S. Products has a nice upholstery machine. Can't recall the name, but it is the wet cleaning only version of the Ultimate PB III.
For many jobs you could also consider doing encap if your budget for a machine was limited. Get a Makita variable speed drill / grinder and a case of Encapuclean O2.