Discussion on answer by jwh20: How should I deal with new trainees when, after a course, they are not able to do even a simple related task?

Simply asking: "Do you have any questions?" is almost always ineffective in my experience. This times a billion. The fact that the actual teacher is doing this is a red flag about the quality of the rest of the course, in my opinion. You cannot ask someone who doesn't realize they've misunderstood something whether they understand; of course they'll say yes!