>>281621679
Thank you for the tips. After messing around for a while, I finally worked out how to do the things you just said. Though I will say that the result from this work isn't perfect. When the leg is bent, the skirt floats above the leg, and I actually needed to go to the top of the skirt's bone chain to prevent clipping, which meant that rotating the leg pushed the skirt into the body. 

It'd be nice if there was just something within Unity where you could tell a bone to start rotating a certain way depending on the rotation of another bone, so that would solve both the problem of the skirt being pushed into the body, and let you only start bending the skirt when the leg is making contact with it.