I've had a similar experience. I occasionally give talks, and often my best talks were about topics where I didn't have to prepare much, because I'm deeply fami

I've had a similar experience. I occasionally give talks, and often my best talks were about topics where I didn't have to prepare much, because I'm deeply familar their topic. It's a win-win situation. Preparation mostly reduces to deciding on the order of topics. Maybe researching some details I don't feel confident about. Maybe drawing some diagrams and/or looking for nice pictures. That's it. The only "trick" is to have an audience to which my topic is all news.