Great resource, but some of the things it references are out of date. To get into Docker Swarm with a solid understanding of how to do things, I recommend Bret Fisher on Udemy.
His Talks are also a great resource:
https://www.youtube.com/watch?v=V9fxU5zJKb4 https://www.youtube.com/watch?v=5zY5_iTGIsU