Write while learning

100% agreed.

At Cambridge, in addition to the lectures, students get small-group (typically two students: research shows three is the optimal number, but the research was done at Oxford so is ignored) teaching called ‘supervisions’. These are done by a mixture of PhD students, postdocs and faculty. Often, students give the best reports about junior PhD students doing this because they still clearly remember not understanding the material. Senior academics who have taught the same material a load of times are also often good because they have seen a large range of misunderstandings.

One of the first reviews of my Xen book (my first book) said that I did a good job of capturing the mindset of a novice approaching the subject. This was easy because my workflow was to learn a thing and then write about the thing immediately afterwards. My second book was about a topic I knew well before I started writing and was less good as a result.