Like Ryan said, using a quality compound will ultimately yield the best results, but the 3M compound at your local oreillys will do. The bottle will designate the contents as a cutting or finishing compound. There are also different types of polishers, rotary, orbital.... A rotary polisher is faster, but an orbital is safer for beginners because if you apply too much pressure it will stop spinning and start vibrating causing less friction, thus less heat.(my tool of choice is an pneumatic rotary polisher) Just like polishing anything whether it be metal, paint or plastic it is a step by step process that can be time consuming. Just take your time, keep the polisher moving, and keep compound on the surface. As a plastics engineer I have plenty of experience with plastic materials!