As many already know, I don't use a buddy-box when instructing, be it fixed or rotor wing instructing.
I've watched many buddy-box instructors attempt to instruct while his or her student is banging away on the control levers. Unfortunately for both student and instructor, this puts tons of strain on both parties, which is more than likely why it is said that instruction can only last for 6-10 minutes per flight lesson.

Why not give the student ground school, hands-on (dry fly) instruction before the plane gets in the air?
Then give the student imagined flight instruction, that way, the instructor can actually watch what the students fingers are doing without putting the trainer in danger. Have the student practice imagined flying while waiting for his turn on the box or any other time.

CCR