I always used to try and get the student to debrief themselves.
Get them to go through the lesson then move onto any points they have brought up then your negatives if they missed anything then positives. The students tended to be alot more negative than you would be so it was very rare you had anything to say bar positive comments. Most lack of knowledge can be nipped in the bud by home work before next lesson.
Hey it worked for me with my students but every student is different.
I always tried to get them to leave with a smile on thier face if not laughing.
It also was quite good for highlighting a good exercise was more luck than judgment.