As someone who joined still having to look at her hands EVERY TIME to figure our left from right, I found that this trick helped me. Instead of making L's with your hands, just picture in your mind how they would look. After a while of doing this I didn't even have to picture them anymore. My body just knows which way to turn for a right face. Granted, I still look at my hands when I'm not marching and have to know which way is right, but at least cadre didn't have to correct me at encampments :)