Here is a decent resource for getting a young quarterback grounded in some solid fundamentals on throwing mechanics (circa 1992). Now, granted there are a few things in the video that don’t lead to efficiency, but, hey…..this was over 20 years ago. You’ll see a young assistant coach named Sean Payton running quarterback footwork and throwing drills.
If you want a great indoctrination of flawless throwing, you’d better invest in Darin Slack C4 and R4 materials.
Darin Slack Quarterback Training