Re: what would you do?
Ha, to think something like this would come back to me in such a way...
I was one of those students who asked the shodan who ran my very first class this, although I had no trouble believing about Aikido's effectiveness before then. I genuinely wanted to know how the strengthless techniques worked. What he showed me was a few simple movements like shihonage that didn't grab the hand but instead used a flowing movement to send the arm flying backwards. Another one he showed me was a simple kokyunage from munemochi (chest grab), where he cross stepped back and used the shift-turn-down movement to throw me into a koho ukemi.
Simple techniques that doesn't require much strength, and they can try quickly without too much training, and of course very practical can do the trick for you. The important thing is that it must end in koho ukemi, since that is the easiest ukemi to learn.