I like to think of coaching coaches as simply making disciples who make disciples.
We all learn best experientially and by modeling. So as the coach is discipled, he or she will go “and do likewise” and disciple the small group leaders. It is a “do as I show you and as you receive” situation rather than a classroom “let me tell you how to do it.”
There will be practicalities that vary (e.g., a coach will not receive regular coaching on small group leadership, assuming they successfully led a small group) but, given that the heart of healthy leadership is a healthy leader with healthy relationships in the home, with other believers and with the lost, those elements will continue to be a focus as they are discipled themselves. They will then continue this focus with their leaders and their families in much the same way.
Sadly, I often see a focus on skills rather than on health. Too often the family of the leader is ignored. Therefore, I like to call true coaching “discipleship from the inside out.” Inside the heart, inside the family, and out to believers and the lost. This “inside out” focus should be modeled to the coach and then continued with small group leaders who also minister to their members.