This feedback task works well with a group or individual.
The trainer re-teaches a section of the observed lesson and the observers have to decide what the differences are between how the trainer taught and the teacher taught. With luck, this will demonstrate how things can be improved. If the observers are stuck and unable to articulate the differences put some keywords on the board to help them focus on the issue you are trying to demonstrate. Be warned you may have to do it several times.
The main issue with this feedback is that on initial training courses you will usually have to do it straight after the observation so no preparation time and you will have to do it with the trainees rather than learners so forgive yourself if it doesn’t go perfectly to plan. I have ended up trying this and made a worse job of it than the teacher!