What are the most universal pitching mechanics that all pitchers must be able to do to have an efficient delivery? Secondly, what drills reinforce those mechanics?
I am sure there are some people that will give you some really good ideas, but this should be in the general advice section, maybe you could repost!
The NPA has a mechanics model that is based on the commonalities shared by most of the best pitchers pitchers in the game. They also have a set of drills to support their mechanics model. I’d suggest getting a copy of the book, The Art and Science of Pitching, which explains all of this. Check here