Wheel and Pc for great finish???

[ALLN1WASH]

How's it going ppl? New to the site and I am absolutely thrilled about all the info and "know how" that's available. I read a few threads an some ppl suggest that the only way to ensure a marred free finish is with the addition of a Pc. I've used a wheel rotary for years and from time 2 time( as I now know we all have) run into a job that down right mind boggling. It sometime seems like, no matter what you do, the darn things just will not go away. Any how, I'm curious the learn a bit more on incorporating the Pc in my process as an addition to the wheel. At what step in the process do you all suggest I break out the Pc, and also which pad is necessary to create this flawless finish.
Thanks for any replies/suggestions...Feed back please