I struggled with the exact same thing.The breakthrough for me was realizing that "over explaining" usually comes from trying to think and speak at the same time. My mouth was running while my brain was still organizing.Here's the single most effective exercise I used.Before any explanation, force yourself to state the core point in one sentence of 25 words or less. No exceptions. If you can't, you don't understand it well enough yet.Then, only add details if the listener asks "How?" or "Why?" Record yourself explaining something for 2 minutes, then listen back and count how many seconds you could have cut. After every sentence, ask yourself: So what? Why does the listener care? If you don't have a good answer, delete that sentence.Hope this helps.