[weekendwarrior]

If you are posting on the professional forum, I assume you are set up as a business, and are possibly insured. I would tell him for liability reasons, I only felt comfortable using the products and techniques that I had experience with from my own arsenal - I would go on to tell him that I don't like to experiment on customers cars, and that's essentially what he would have you doing using products you aren't familiar with. I would also tell him that I charge by the hour, and will be much more efficient using products I am use to.

If he still insists, I would move on to the next customer. This guy has already raised too many red flags, in my opinion, that lead me to believe he will be more trouble than he is worth. I think you could do a killer job on the car with your own products, and he will still probably badmouth you to other people and say things like, "He did a good job, but not as good as if he had used my products."