Sometimes I work with really good presenters that already have a really good presentation. How to get from 90 to 100%?

My approach would be to sit in the audience of a real live presentation, or watch an entire presentation from start to finish on video. Then, create a series of slides that exactly mimic the story. Take out slides that do not really add anything and are just a prompt for the presenter to tell a story. Add black slides to switch off the projector all together. Use very simple graphics and words to support a story. Be a movie director and look at each frame of presenter and slide together.