Might look like self-promotion but a tool* I've developed is meant to help (read: force) people into writing in a better way:
You write your full idea, then you create a new 'layer', and have to cut down on words. Basically distilling what you're trying to say. In the end you'll end up with the 'shortest' layer of the message.
I built it partly with the aim of helping remote workers 'learn' how to write better