When it comes to writing, I write it out, and then I tear it down to size. My writing is better than most people’s but it takes time. Any good writing from anyone does.
As for speaking that was always hard. What helps is not worrying so much. If I’m speaking in front of a crowd I have a list of points that will connect my thoughts. I try and make it through the points. If I miss some I don’t worry about it. Not sure I’m a good speaker but a lot of people appreciate the fact that I don’t give the usual boilerplate talks.
In either case, give yourself a time limit and stick with it.