Question on the Porter Cable...

I've read tons of posts here and on .org about how great this machine is- and how it can polish out swirl marks and micro-scratches. Given that I have a jet black car with tons of tiny scratches (that show up if you look really close), this sounds good.

I'm wondering though-- is there a limit to how much you can polish with this machine and not damage your paint? I've read articles that say you can press on it as hard as you want and it won't burn through paint like a regular orbital buffer. Is it ok to use something like this every 2 weeks?

Also, despite using freshly washed made in USA terry towels to dry the car, I still get scratches and swirls. When you guys say that you meticulously detail your car and don't get these marks- what towels/cloths/mitts do you use? I'm also very careful to not use a circular motion.