When you say swirl marks you must be talking about burn marks. These are huge visible swirls on the paint that are caused by an amateur using a professional polisher wrongly! These polishers just spin on their axis at varying speeds and you can literally take the paint off with them. You really have to know what you are doing with them.

If you are an amateur you want something called a Random Orbital Polisher/Waxer. The circular pattern of the head along with the circular motion of the tip will not cause you to burn the paint and its idiot proof. You can buy a cheap one like Rahulio1989300E did above or you can buy a Porter Cable which is widely known to be a pretty good make. Just make sure it says Random Orbital!