Okay... let's see if I can outline and answer questions in one shot
The first shot in the thread is after it has been washed, driver's side rear door (as I mentioned. Front door looked the same, as did the whole car, although I forgot to take a pic before I did it. Anyway...
I had experimented on the hood with yellow pad/PI-III and it still left some scratches that I felt could come out, scratches along the lines of the swirls, not some of the ones that won't come out without wetsanding.
So on this door I went with the wool pad that came with the PC, I think from Coastal Tool... although Zenhog could answer that as I bought it from him.
I applied the PI-III, just put it on the wool pad, and rubbed it on the door... working on about a 1'6" x 2' area (basically from the top of the plastic to the window, and from the front of the door to the front of the handle on a 98 Jeep Grand Cherokee)
I worked it until it was nearly dry... and wiped it off... it wasn't quite how you see it, picture about half as many swirls, but not as deep. I deduced I had been working on too large an area, not enough pressure/product.
Applied PI-III again cutting it down to 1'6" x 1' and applied a good amount of pressure and moved alternately between fast swipes, and slow. I was applying enough pressure to noticably slow the PC down, but not to just vibrating with no rotation (I worked with it on 6). Worked it to near dry, and wiped off.
I honestly didn't really look too close after this, and moved on to the white pad with MG... same process basically, except I slowed the PC to 5 and didn't apply as much pressure, slightly more than just resting it on the door.
I have since done the rest it, although only with the wool pad/PI-III combo. I will take a pic when my roommate gets back with his digicam. I de-badged and used just the wool/PI-III where they used to be as well... honestly, it looks nearly identical to the third pic I posted, I can barely tell a difference, although I'll check it out more closely when I get the digicam.