I'd love to hear what the guys on the CFICast think of this. I bet they'd have some pretty strong opinions.....
Well Tony, whose post is just above you, would be one of the ones commenting on the CFI cast. Reading between the words, I kind of have an idea what he might say.
Normally, it is pretty difficult to get a prop to stop. You have to be going pretty slow. In the original post, the OP said they were doing stalls when the CFI pulled the mixture. In that case I would suspect that the prop WOULD stop unless the nose was lowered and speed built up rather quickly.
I don't think pulling the throttle to idle is a very realistic simulation of an engine failure. Likewise, I think pulling the mixture isn't really a good simulation. I mean really. The student sees the CFI pull the throttle, or mixture, he immediately knows there is an "engine failure". Given THAT choice, I would advocate using the throttle rather than the mixture.
Having said that, how does the brain trust propose a good simulation that introduces the surprise factor of a complete engine failure? How about something less severe, such as a bad mag, or carb ice, or any of many other reasons for power issues?