Agreed mate, JD and Gally seem quite incapable of realising that the vast majority of people in this country, and even a big percentage of those into cars, have never felt the need to start attacking the paint on their car with bits of clay.
My first first-hand experience of it was my mrs used some on my daily corsa about 2 or 3 years ago as it had a load of angle grinding sparks in the paint where I had been making up some big brakes far too close to it for my mk1 using a grinder and I was genuinely amazed at how it managed to lift out metal that I had assumed was properly burnt into the laquer and I was destined to have a rusty metallic flake in forever.
Its a cool product, and actually very easy to use, have done it myself since, but im sure your man has the ability to fly around a car and do 80% of the job my mrs or JD etc would do but do so in 20% of the time, which is a skill thats very useful for providing a decent valet (lets not say detail again as it annoys JD)