Re: man, it's tough!
Totally agree. I've only been teaching for about 4 years, but doing something and trying to explain why and how you are doing something are completely different things!
I used to do a funny joke sometimes with a particular student in demonstrations. I always knew he would try and resist the technique i would try to put on so I would always say the converse of the technique I was actually going to do! e.g. I would say I was going to do morote-dori kokyu-nage/sokumen irimi-nage. As he leaned his full weight on my arm holding it down, I would just do kaiten-nage - it would always look like I'd done the most perfect throw, just because I could predict where he was going to apply the force!