A simple polishing wheel on the end of a drill should work just fine. There is a recent commercial out for a buffing pad, I don't recall the name. Polishing it should not affect the balance, you couldn't possibly remove enough material to throw off the balance. However, if the blades were polished differently (one shiny, one not so much so) It will effect the prop performance.
If your doing this for "looks" then I wouldn't even attempt it.
Function over form, with few exceptions.