Listen to the Dr.
Just be carefull not to set your TAS as your track. Seem's simple but I was checking a pilot to line on a King Air and he had 6000 + hours, grade 1 M/E instructor rating and he set the TAS and I did the same on my PPL flight test. I was lucky setting 120 instead of 125. It was a very short sector and I was within the tracking limits. I only realised the error when I set the next track!!. Do some "back seat" Nav's with other students if possible. Take your WAC charts and a copy of the flight plan. You can do a NAV and the other student "back seats" yours, well that happened in my day!!
Best of Luck
Rifdas