The biggest problem I've found is that the feedback loop is too long if you play a whole game and then go back to discuss it (especially when playing in person

The biggest problem I've found is that the feedback loop is too long if you play a whole game and then go back to discuss it (especially when playing in person without a record). It often works better to stop the game and talk about why a sequence of moves was particularly good or bad, and play out a few variations immediately. Depending on how well the student is doing, either continue the game from the original position or the best alternative.