The broadcasting doc is surprisingly readable and easy to follow. And the rules are surprisingly simple. The diagrams and examples are excellent. https://numpy.org/doc/stable/user/basics.broadcasting.html

After taking the time to work through that doc and ponder some real-world examples, I went from being very confused by broadcasting to employing intermediate broadcasting techniques in a matter of weeks. Writing out your array dimensions in the same style of their examples (either in a text file or on a notepad) is the key technique IMO:

  Image  (3d array): 256 x 256 x 3
  Scale  (1d array):             3
  Result (3d array): 256 x 256 x 3

And of course with practice you can do it in your head.