lol graco, i used to work for a groomer who uses one, and she is the only one i have ever seen.
honestly, i did not like it. and 40 dogs? um no. to effectively wash a dog with this thing, you can get about 25, maybe 30 (which i guess is still a lot, but not 40). i remember on busy days (at that salon, busy was 40+ dogs), I always had to refill it. if you do stretch it out (my boss was getting mad at the extra shampoo bills), you end up having to use other shampoo, and just the prima for the all around body parts (which is pretty much a waste). or i would do one really quick spray down with the prima, then a really good shampoo with something i mixed (again a waste). i didnt like the nozzle, it never could get deep into heavyduty coats (the way the hydrosurge does). and it is really annoying being attached to a cord to a machine. maybe others like it, but i really didnt.
i have used hydrosurge and the bathing beauty as well and liked both of those much better.