To get back to the original question:

I shoot a variety of cameras. Some were "uncomfortable" until i realised there is no law that you have to use the right index finger! I often use the right ring finger with small cameras, especially the Bessa-L which I don't really need to aim. I hold the whole thing in one hand, with the ring finger resting on the release...

The Bronica ETRS I use the long finger, except in portraid which is best with the index finger. Some old folders are definitely easiest with the thumb - plate cameras especially so.