Master your breathing. It might sound too easy, but speaking mostly while exhaling has really helped me with stuttering. Remember those blocks you get when stressed? Turns out you won't get them(as much) if you exhale, especially deep breaths using your diaphragm(used for singing as well). Also, you will talk slower/more methodically. It is all connected! Since you mentioned Propranolol, I have tried that, and not too happy about it. It did make me calm down, but the stutter was still there.