Lol, brings back some painful memories from when I first switched over. I was so paranoid on first cleans (switching trad cleaned to wfp), it would take me ages. I think I worked with a flow around 20 - 30 or so and that was about the norm for first several months until I came to my senses, well got sick of it taking ages. That I started experimenting with varying techniques and flow rates. After that I started experimenting with various jets/jet sizes/number of jets and different brush types. The amount of time and money I invested back then was crazy, but worth it.
He'll either improve or sack it off n sell up