growing rock star employees as managers

you've got some young, talented employees in a growing startup and they have the potential to manage a larger group of employees as the startup grows. what are some great ways to help them do this? what have others found to be helpful, especially in a chaotic startup culture where there isn't always time to provide more formal training or training beyond example.

Possible location - WeWork building (have to see what they charge) on 2nd betw Mission and Howard