Unless you are a real PRO at using a rotary buffer (it's amazing how much damage can occur so 'effing quickly...) I would suggest an orbital.

You can find a Porter-Cable 7424 for $120 or less. There are 2-3 other brands with the same capabilities and reliability.

I suggest you look through the videos here:

Car Care Forums: Meguiar's Online - News & Announcements

A whole lotta' good info to be had...