Not really commenting on the guide, but for me, clarity of thought follows writing. Not the reverse.
1. Think that I know something.
2. Write about it. Realize I didn't know it anywhere near as well as I thought.
3. Reflect on and actually understand thing.
4. Edit writing now that I actually know what the hell I'm talking about.
Writing for clarity often involves careful consideration of how to sequence the information such that it can be consumed given the audience and knowing when to elide details or otherwise footnote them.