I first saw this documentary a few years ago on youtube, but it was taken down because of copyright laws. I'm super excited because I just found all the parts again on dailymotion! It's a long documentary, but my advice is to watch it before it gets taken down haha. You'll learn a lot and it's fascinating to see how the movie is produced. It's also one of the only sources I've found that shows how Miyazaki draws.
Link to part 1: