I use BBF with single point autofocus set to centre and eye/face tracking (for living creatures). Removing the focus from the shutter button does not necessarily stop the shutter button from doing metering - it depends on what you select. However, I prefer to use Centre Point Exposure for MY purposes, as I shoot wildlife in a lot of highly dappled situations, so I need that level of precision, and one cannot assume that the place that has a mid-reflectance is the point one is focusing on. Thus I have the * button set to AE ON-OFF.
In this example, I was literally shooting between the leaves and branches and the panda was moving about.
I don't use the joystick to move the focus point around, as Bill (Waddizzle) said, it's too slow and if I did I would use my thumb on the joystick rather than move my finger off the shutter button - I use my thumb to lock both focus and exposure. If you are using eye tracking, then once the focus is locked it should follow the subject. That said, focus can get fooled, certainly by dense obstructions, so (again using my thumb) I can re-centre the focus point using the OK button, or if you prefer pressing in the joystick button.
So, in order of events: I choose a point that has the right reflectance and place it into the centre of my EVF, and press the * button to lock exposure
Locate the eye, or other strategic part and centre on that, press the AF-ON button. Depending on the mode I am working in (may not be face/eye tracking) I may be using Servo focus, and holding down the AF-ON will track that point for a dynamically moving subject, as opposed to a simple tap that holds that focus distance for a static one. I then recompose and take the shot using the shutter button.
I have different scenarios assigned to the C1... C3 buttons for tracking or otherwise.
Once you get the hang of it, it's extremely fast and the only phalange that has to move around is the thumb, leaving my finger always poised above the shutter button ready to take the shot. It works for me... FWIW.
