[jrow]

89notchback,

First off as far as equipment goes, I would buy the correct equipment fit the job your going to do! If you're going to polish a valve cover that doesn't have all the nooks and crannies in it then a bench mounted buff would be best. If you're going to polish an intake manifold that has all the nooks and crannies in it then then a die grinder would probably be best.
What I've done is, I bought an 8" bench mounted buffer, 3600 rpm, and use 10" wheels on it. I also use a 3/8" drill motor, 2500 RPM's with anything up to 4" buffs on it. I also have an electric die grinder that I have attached a router speed control to that I use smaller buffs and cartridge rolls with, and I have a Dremel that I use for really small areas.
I prefer to use chucks without keys as I don't want to tape them every time I change bits.
So as Baz has stated before look at what you are going to do, make a plan and go for it.
I'd start with a 3/8" drill motor and go from there. It will get you started and if done properly it will give you good results!
If your buffs are scratching get new ones. You can wash them but thats not saying that you will get out what is scratching your metal. I use Acetone to clean between compound changes.
John