Jack Dennis is putting a lot of nice commercial videos from the late 1980's on his YouTube channel. I watched a lot of those videos back then, often not so good screen quality being copies.
Here's a video, Introduction to fly casting with Terry & Wendy Gunn, on fly casting instruction that's new to me. It's a pretty easy going yet quite elaborate. It basically handles all the basic casting one needs to know. It's also interesting to see how this couple (Terry & Wendy Gunn) have different casting styles. He has a more vertical and shoulder motion casting movement while his wife Wendy has a more side angled and elbow casting movement.
In my opinion the shoulder casting movement is a lot easier to learn as the movement is '2D'. All the movement are moving in one plane, just like how you move your arms when you're running. The Elbow casting movement is a much more complex '3D' movement as it involves your elbow, upper arm and your shoulder moving in different directions.
One casting style isn't better than the other but it's something one should be aware of as your casting level reaches a certain level of competence and you start to teach beginners with their casting. You should know how to keep your casting instructions consistent and not to confuse the student if what you're telling doesn't correspond with the casting movements you make.
Update Feb 3, 2021: This video has been removed from Youtube. Jack Dennis sent me this message: