If these are 12 V portable testers, that improves our ability to find intermittent problems. This is a simulated road bed, allowing your car to be driven while it is tested without leaving the service bay. That training required is more a way of thinking than anything else. We already know a good technician has above-average intelligence, high skills in math, science, and comprehension. Now add chemistry and it gets rather interesting.
Information is the key to unlocking the mysteries.
Information sources must be available and of high quality. To prepare a technician for a potential emission diagnosis they can be taught by a trainer in a classroom, use an interactive CD, a video, book, or magazine articles. One time, the first time, and only replace the parts you need, not everything under the hood. My trip to Aspire helped me see the future. In the next 10 years we will have cleaner air, but many shops may go out of business because they fell behind.