https://www.youtube.com/watch?v=hIU I6ZdkLA4 Hey, how do you

Looks like an awesome way to get RSI real fast.

I agree 100% that you should use the rocker switch. It is incredibly useful. How you map the buttons is up to you, but I use one as Right Mouse Button to quickly switch brushes and brush size, and the other is the Alt key as super quick eyedropper tool.

However, the way he's holding the stylus looks super awkward. I would recommend holding the stylus like a regular pen or pencil.
Let it rest naturally and loosely on your middle finger (close to or on the first knuckle) and the crook of your thumb, using the tip of your thumb to hold it it place. You don't need to exert any force to keep it in place. This way, the middle finger is already free to move, and it is super easy to lightly tap the switch whenever needed.

I've been using a tablet for about 15 years, and never had any strain or discomfort.