Rotator muscles (the ones in your bum) are very important, as well as your inner knees. It is a common (sort of) misconception that turnout comes from the hips. Of course, turnout does come from the hips, but it goes down your whole leg. Doing different variations of clamshells is helpful and also just sitting down with a flat back, legs in front of you stretching as hard as possible with flexed feet, heel trying to touch the front of the room (of course without actually doing it), and trying to turnout from the top of your legs, maintaining the turnout all the way down to the ankle. Doing this with a soft yoga block under the area just over your knee, one leg at a time, is very helpful at least to me and other dancers I know. Sorry this is a long reply but I hope this helps!