I've done a lot of playing around with chemicals over the last couple of years. Here's a little of what I have learned:
1. For MY area (ie: dirt types in my area) LOW-HIGH has ALWAYS worked better no matter what the chemical salesman tells you. You need to experiment for your conditions. This may also change at certain times of the year, but I leave it this way always now.
2. You want the second pass to be strong enough to swing the pH past neutral. In my case, it goes way high, which isn't that great for drying, but I take care of that with CCP. Rinsing well pretty much gets you at least to neutral pH anyways.
3. Don't ever trust labels/ starting point titrations, especially if someone is quoting you per car costs. You MUST do your own volume calculations to figure out what you are paying per car.
4. Titration starting points are just that- start there, and then increase concentration until you are getting clean cars. I watch HUNDREDS of cars before deciding if things are good. Touchless can sometimes be hard to judge since you can never clean all cars 100%, and everyone's idea of "clean" is different.
5. If you are going to do touchless right, you have to use soft and hot water. You can also get some better results at certain times of the year by increasing your soaking time. I do 10 seconds for easy times, 15 when it gets tough.
Kurt