I suggest you train them to run a constant radius test. Pick a radius that consumes almost all the engine power you have. They need to be so smooth that your test data looks analytic. Teach them how to read the test results and get from them engineering feedback in terms of "better" or "worse" from nominal. Since its the same 'car' all the time with different suspension settings, parts and tires and pressures, train them to read the tangent speed. That way you will know when the car is getting better/worse without chewing up the tires. Use the ISO4138 procedure. The calculation of front and rear axle sideslip gains will tell you which setup is "better" or "best". If the driver can't be smooth during this phase of development, they definitely won't be any good at the end.