Demonstrating the throttle during Exercise 4 is EASY with the governor on - after all - it's been designed so that you can override it by hand.
So leave the governor on and simply explain to your student how it all works, how it can be over ridden and make minor adjustments to the throttle by hand (even keeping it within limits results in enough of a change to be seen). Simples.
You can also show how the governor works when you start the aircraft by letting them see during the run up how the governor kicks in at 80% and then maintains things in the the green at the top end.
So everybody on here really is in a flap for no real reason other than a poorly titled thread.