Please tell me I'm not the oldest in here. I did mine in the early 80's it was a the seagull Mk5, a modified Boeing 707, astro nav and grid nav on a mercator was still in the syllabus but being phased out. I did it fulltime at tafe in sydney, the lecturer was an ex QF navigator named Doug Nolan, a delightful guy. He enjoyed a 100% pass rate.
IMHO, there is no substitute for rule of thumb, if you can calculate a heading and time interval from any point in space to an adequate runway and fuel required/remaining in less than one minute in your head, that's all you need. The same applies to a PNR. Keep it simple. I don't see a need for ATPL flight planning theory at all, the subject material would be better served if it were heavy jet principles of flight.