I signal turns with my left arm, as I learned 60 years ago, as long as I have an arm free. I don't think anyone, including cops, recognizes it. People wave back.
A few months ago my shoulders were stiff. While waiting to cross a busy street I took the opportunity to work out the stiffness by raising them above my head and moving them around. A bicyclist waiting to cross the other direction asked me what I was signaling.