Good tip
I'm doing various shoulder stretches. Keeping my arm perpendicular to the body, while lying down on the floor, rolling both face down, and partially face up, depending on whether palm up or down and whether going left or right.
Also do bungee rope work - gripping in front of me, pivoting over my head and down the back of - sort of a butterfly stretch.
Another is lying on my back, holding a heavy kettle bell in my arm, raised straight up, then turning that shoulder up and down while balancing the LB.
Next is the towel thing to work my way toward being able to grip hands behind my back.