There are two students in my current divemaster class. They are naturals in the pools and it has been a lot of fun working with them on the various skills that we have cover. Last night, I sprang a surprise on them. I have a non-diving friend who was visiting me and I suggested to him that he accompanies me to class and be a discover scuba student for the evening.
The two candidate divemasters had to walk my friend though all the steps of setting up the gear. He didn't have to set up any of the gear himself, but just had to watch and learn. The candidates did a fantastic job. One of the candidates has a great way of explaining concepts in every day terms and makes even seemingly complex things seem easy and understandable. They seemed to really enjoy the unexpected challenge.
The advantage that I could see was that they had an actual person to demonstrate the skill to which probably made it more realistic for them. In any event, they will make excellent instructors one day.