All painting is is learning the techniques. All paints have their own ways about them. I had always used Dupont, and had no problems with them. I was used to them. The painter I work with used Diamont, and was used to them. We both recently moved to a new shop, that uses SW. He was hesitant to change jobs because of the new product. It took him a little while to get used to it, and still has some setbacks. Fortunately he doesn't have to pay for materials when he makes a mistake, but he learns from them. I recently used some Debeers base coat, and Upol clear, because it was supplied with the vehicle. I had nothing but problems with it. I am not saying that there was a problem with those products, just problems with me using them. I guess we hadn't been introduced properly.
I was fortunate in that SPI carries the exact color that I was spraying, so I was able to replace the other product without breaking the bank. That SPI product was more agreeable to the manor that I spray.
Keep in mind that a shop usually has the set-up to make more materials, in case of an error. That means that the painter will quickly learn that product if he is new to it. Working with a new product away from that environment, like when it is purchased just for a specific job, there isn't that safety net.