When I do my demo (usually of meat fabrication that sometimes takes a bit of idol time) I ask questions about what they were suppose to read last night and bring up points that I know will be on the test(s). Occassionally I'll get the deer in headlights look from them so I'll say ok "let's start at the beginning" So instead of just telling them the answer, or telling them they need to go read about it, I go back to a point that I know they know (backtrack basically)and start asking them questions that they know/ can figure out and let them lead themselves to answer my original question (with a little help from me if needed).