For me it is difficult to give good code comments just when code is written. The problem is solved, the tricky parts if any are internalized. I dont mind reading code so just documenting what the code is doing does seldom bring value. The important thing is to document why the code does things in an non obvious way and unintuitive scenarios and edge cases etc.

When revisiting code is the best time to add comments because then you will find out what is tricky and what is obvious.

Code reviews are also good for adding code comments. If the people reviewing are doing their job and are actually trying to understand the code then it is a good time to get feedback where to add comments.

There is a hack for that: write the comments before and/or as you write the code. When things are still unclear, weird. Of course do a final pass on them to ensure that they are correct and useful in the end. This is one example of document as-you-go, instead of doing it after "the work" is done. I find it generally leads to better outcomes. Doing documenting only at the end is in many ways the worst way to do it.

Here's my method, which is a bit similar to the siblings.

Your first "docs" are your initial sketch. The pieces of paper, whiteboard, or whatever you used to formulate your design. I then usually write code "3" times. The first is the hack time. If in a scripting language like python, test your functions in the interpreter, isolated. Then "write" 2 is bringing into the code, and it is a good idea to add comments here. You'll usually catch some small things here. Write the docstrings now, which is your 2nd docs and your first "official" ones. While writing those I usually realize some ways I can make my code better. If in a rush, I write these down inside the docstring with a "TODO". When not rushing I'll do my 3rd "write" and make those improvements (realistically this is usually doing some and leaving TODOs).

This isn't full documentation, but at least what I'd call "developer docs". The reason I do things this way is that it helps me stay in the flow state, but allows me to move relatively fast while minimizing tech debt. It is always best to write docs while everything is fresh in your mind. What's obvious today isn't always obvious tomorrow. Hell, it isn't always obvious after lunch! This method also helps remind me to keep my code flexible and containerize functions.

Then code reviews help you see other viewpoints and things you possibly missed. You can build a culture here where during review TODOs and other similar things can be added to internal docs so even if triaged the knowledge isn't completely lost.

Method isn't immutable though. You have to adapt to the situation at the time, but I think this is a good guideline. It probably sounds more cumbersome than it is, but I promise that second and third write are very cheap[0]. It just sounds like a lot because I'm mentioning every step[1]

[0] Even though I use vim, you can run code that's in the working file, like cells. So "write 2" kinda disappears, but you still have to do the cleanup here so that's "write 2"

[1] Flossing your teeth also sounds like a lot of work if you break it down into all subtasks 1) find floss, 2) reach for floss, 3) open floss container, ...