I've used all the PowerBalls -- including the cone and the one for paint, and I love them.
They can take a little finesse.
If you're doing a finishing polish, use little pressure or all you're going to do is scratch the finish (which you can also do by hand).
Run the drill in low speed range (300-400 max) and a medium clutch so it slips in case you jam it somewhere it's not meant to be jammed. You will probably need a decent 18V drill, or if you have one of lower voltage, if it's high-quality you should be okay.
Speed is not your friend here -- if you're slinging polish, you're going too fast.
Work an area at a time, using enough metal polish to keep the ball or cone lubricated and create a buttery black residue. If you do have to use pressure to remove oxidiation, finish with light pressure. Wipe gently with a microfiber towel. Too much pressure or too much speed and you're not going to do any good.
If your ball is tearing up on an edge, work the angle so you go the opposite direction against the edge.
If you're still having problems, you might want to see the tips
here.
There is a satisfaction guarantee -- so if you don't like it, you can contact Mothers for a refund or for tech help.
One more suggestion: disassemble it and wash it in dish soap or in the washing machine. Make sure it's clean, rinsed thoroughly, squeeze it dry and let it air dry for a few days before storage.
Here's a video I found on youtube: