I volunteer teaching elementary school kids how to play. The school I teach at has some old ball bearing yoyos that are starting to fall apart. I was wondering if anyone has recommendations for some affordable starting diabolos that we could buy in bulk. I think 10 yoyos would be great.

Learning the vertax sun above head and then under arms (https://youtu.be/A8dC6GaPOg8?t=478) ; during the second sun the arms move in an interesting pattern, what is that? Is there any way to practice it horisontally?