Comment by alexpotato

I find that writing this documentation is both a "muscle" and gets better with experience.

e.g. as you both write documentation and see yourself or others use it, you start to get a feel for what people tend to understand and how to communicate it.

You can also do "dog fooding" where one person or group writes the docs and then other people follow them. If you iterate on this quickly, you can get to really good docs in a short amount of time.