Until I get a bench grinder like Oscar's, I'm still stuck with the drill trick.

I've seen several people mention putting the handle in a drill and using stainless wool to get off the rust. I tried that, and found that it did remove rust, but also scuffed the underside of the ball to a dull haze, so watch out for that.
Grasshopper: Which car stuff did you use? The stuff sold as "Rubbing Compound", or "Color Magic", or what? Did it affect the balltop plastic at all?
Anybody/Everybody: What are you using to polish the knob plastic?