For cars with "normal" basecoat/clearcoat, that is, NOT as hard as Audis have (or Mazda silver, that stuff is *HARD*, like white single stage Imron!) just go with the "usual" pads from Lake, Meguiar's and Griot's.
Lake pads are available from CMA and TOL. Meguiar's pads are available MANY places. Griot's pads are available from Griot's. When used with a PC, the subtle differences between the different manufacturers' pads ("variable contact" vs. flat, etc.) really aren't very significant.
As TOGWT said, the regular "white CMA"/"polishing" pad is the general choice for most operations. I haven't tried their "orange power pad", but opinions on it vary. The equivalent polishing pad from Meg's (pn 8006) is also good and is the usual choice fo those who prefer Meguiar's products. Griot's orange pad is a bit more aggressive than either of those, but still not TOO aggressive- I myself really like it for a general purpose polishing/glazing pad.
For removing REAL swirls and minor scratches, you really need a "cutting" pad, like the Lake/CMA yellow or the Meg's burgundy (pn 7006, as I recall). The PC is SO gentle that these pads are often (usually? *I* would say so..) required to remove the sort of marring that most people deal with using the PC.
As far as products go, for Audis I've had good results with 3M and 1Z. There are a lot of other good choices out there, but these are the ones *I* have had good results with. I especially like that they don't need to be worked too long for their abrasives to diminish to the extent that they do.
I use 3M's PI-II (pn 39002) and PI-III (pn 05933) FCRCs and PI-III MG (pn 05937). The 05937 is sorta the "standard recommendation" product for many applications, but it's usually a little too mild to remove ALL of a car's marring, hence the RCs- which are milder than most people might expect. If you have trouble with polish residue from the 3M stuff, you can remove it with Final Inspection or AIO.
I've recently started switching to the 1Z line of polishes. The Ultra (most aggressive) is good for mild scratches, but you MUST follow up with a milder product as it WILL leave marring of its own. It's more aggressive than the abovementioned 3M RCs. The "regular" 1Z polish is "Paint Polish" (in the green can). Similar to the 3M MG, but easier to use (no hard to remove residue). The mildest 1z polish is "Metallic Polish" (in the red can)and it contains a little wax. It is VERY mild, don't plan on removing any swirls with it. The 1Z polishes have a LOT of oils and (I think) some fillers, but that shouldn't be a problem unless you're using Zaino (then you'd need to remove the oils after polishing). I've put MANY different final-step products over the 1Z polishes and there were no problems with bonding or anything else. All-in-all, I really like the 1Z polishes.