Greetings, fellow Sony shooters. I'm on a bit of a crusade because if you're a back-button focus fan like I am, there's a pretty good chance I can give you a better way to set BBF up than you're doing it now.
It's basically a way to autofocus when your camera is in manual focus mode, so you get all the benefits of manual focus, plus the ability to autofocus with a single Custom Button press (no need to switch between focus modes). While setting it up isn't hard, it's definitely not intuitive. But once you do it, your photography life will be much easier. Try it and let me know if you have any questions.