aces - the idea of ADF tracking could well be introduced to the VFR guy as well.
Start them off doing radio navigation under VFR - it doesn't HAVE to be done in instrument conditions (save that for later - once they HAVE the mental dexterity). They can even log it P1 if they have their PPL - and that will make you very popular (even if you are being paid for your time).
Get them to buy a copy of RANT and they won't even have to hold height (height?? - altitude) and track until they have 100% "sussed" the concept.
Not forgetting, of course, that radio tracking is part of the PPL training (and test).