From personal experience i never expected a conversation with anyone on the door to door ministry. I was almost always cut of by the time i got to: "Hello there, my name is XXXXX and we're just..." that was as far as i'd usually get before being told they wernt interested in which i happily took my leave. (No effort on my part to throw in a counter phrase like the demos).
I think this is likely common in my area so most witnesses will likely be unprepared. For my next visit im asking about 1914 and for an explanation from the bible alone. I know for a fact only 0.01% of them can explain it off the top of their heads.