Coincidentally (or not!) we covered this in my lesson today. Sooo interesting! What I took from the lesson regarding outside aids was mainly that I need to be much softer. Hands have to give, not be fixed, but the main thing was that I have to use my legs very much more than I tend to do (in an intelligent way, not a harsh way).
Turning is much more effective if I use both sides of my body. My lazy tendency has been to rely on inside leg and inside rein to make a turn. Today I learned that I got a far superior turn using both sides of my body, shoulder, hand, hip, seat bone and leg both sides of my whole body. You need a floppy bottom to get your seat bones to move softly, you need to support with your outside leg as well as weighting your inside leg and you need to turn with shoulders and hips round the turn too. Oh! ...and unfixing the contact in your hands starts from your shoulders too!
Brain is a bit tired now though....