ST,
Great suggestion. I hadn't thought of that "trick" before.
Concerning carb icing, I had never experienced it prior to coming to Canada. The main reason for that was the RAF Chipmunks that I mostly flew in the UK had the carb heat wired in Hot.
My first experience was solo, flying a 172 from Calgary to Banff. There were some clouds ahead with virga underneath, so I thought I would do a carb ice check. When I pulled the carb heat control out, there was instantaneous rough-running that was so bad that my instinctive, inexperienced reaction was to push the control in!
So the moral of the story here is that students should get their instructors to show them the effects of carb icing on a suitable day, preferably within gliding range of a suitable landing area.
I agree with your comments about the carburetor temperature gauge. I've just started flying a 182 that has one and it is very comforting to be able to glance at the gauge and make sure the needle is not on the yellow arc.