sorry for asking soo much questions regarding cleaning, since i just bought a black 2000 gs3, its so hard to keep clean but you gotta love the blaCK when its washed, however i was wondering how often do you machine buff your car, and what is the purpose of using one of these ? thanks...

 

I do a complete detail once every spring. I polish with the Porter-Cable using Meguiar's #80 or #83 and then #80 if the marring is deep. I would not worry about doing this twice a year if needed. I pay a good deal of attention to not marring the finish as I maintain the vehicle during the year.

The purpose of polishing with the PC is to remove any swirls and oxidation.

 

I use my PC on my car once every few months to remove whatever light swirling the paint's accumulated since the prior polish. Keep the swirls and marring to a minimum by using proper wash techniques.

Check out http://autopia.org to learn some more.