Below is a link to a lovely and informative article on the muscles of turnout presented by The Ballet Blog. This article is one of a three part series called Training Turnout.
It discusses the function of each turn out muscle and its role in ballet positioning, as well as the improper griping of the gluteal muscles that can actually decrease one's turn out. These articles also highlight exercises that can help train the correct muscles of turn out and when to perform these exercises. I hope that you find it helpful!
CarliAnn & Ella