It’s possible to turn the shutter speed dials on the old photomic heads using only your index finger, but you have to push pretty hard. Some people like using a raised soft release (like the AR-1) so the trigger finger rests closer to the shutter speed dial. Personally, I don’t find it disturbing to use both my thumb and index finger to turn the shutter speed dial while looking through the viewfinder. I don’t use a soft release; I like to rest my trigger finger on the collar surrounding the shutter release, using it as a kind of stabilizer. It works well for me.
Remember that with the F2, shutter speeds below 1/80 are full stops only.