Since you have a shoulder problem, you are much better off buying a Porter Cable buffer and some quality detailing products to make your job easier. Everyone has their own favorite brands, but some are a lot easier to apply. I used to be an avid Zaino guy. Loved the end result but did not like the time and some of the steps in their process.
I found that with Adam's and a PC I can detail any of my Vettes (wash, clay bar, polish & wax) in about 2 hours. Plus, my arm is not falling off when I am finished. The PC is really great for this. You can get the PC at most Home Depot's and Lowe's. Adam's also sells them, plus he has a quick disconnect for the PC that allows you to use a double sided pad (each side has a different level of aggressiveness for a specific application). The PC is really easy to handle, does not wear out your arm, and is very quick.
I have a power ball that I occasionally use for my wheels, but I typically only use it when I take the wheels off to do a thorough detail on them. I would not attempt to use the power ball on your paint surface. I just don't think you would have the ability to control a drill with a round object as well as a PC with a flat pad. JMO.
Rich