In an R22 there certainly is quite a force on the collective imparted from the check pilot who has to overcome the throttle friction. It's always wise to establish whether that will be an impediment or confusing to the trainee or not first.
To get around that, one could always go through the routine a little differently, but always only after the warning that at all times one has to be prepared etc, and discuss whether;
1) there is enough airspeed to help RRPM recovery if necessary,
2) we are safe to reach an area,
3) cover the collective with left hand,
4) say "throttle in overide check" as the switches go off with the right hand and straight back to cover the cyclic if necessary.
Next time just kill the switches. Forget about being tired, especially when the subject is tired or wound up is a good time, then you know that he/she will/can respond anytime.
In a 47, non turbo of course so one doesn't root the turbo, during the silence one can usually have some time to discuss the subjects heritage for a while before taking over, if it's a bit slow working it out.