I just tried it.
It reduced my tinnitus considerably, but my torn rotator cuff is now screaming at me. It did NOT like me having my arms in the required position.
That’s a minor problem, though, because I’m sure my wife and/or teenaged son will be happy to cover my ears and thump me in the back of the head...
I have arm problems too. Tried that method and couldn’t hold it. I then decided just to use only my good arm and simply tap on that area with my thumb. Works immediately for me. Ringing goes away for a long while.