This is a great tool for the writer as well when developing and writing their characters expressions and thoughts. It doesn't have to be "he said, she said". The psychological gesture, in acting, in writing, and in real life, is the core of and revelation of "character". It defines the truth of who we and our characters really are.
Become an observer and watch the gestures. Write them as an actor would act them. Gesture is everywhere, in everyone, always. What great characters are hiding behind gestures?!