What to buy? Did you get the 5" backing plate for the PC? If not you NEED IT.
Depending on your paint, what shape it's in, if it's been sanded before, is it single stage or bc/cc, and of course hard or soft.
From there it's about what speed you run your machine, pad speed, arm speed and of course arm pressure.
You'll also need a supply of pads. First time around with neglected paint (that say is on the hard side) working with the PC and 5½" pads you can probably get away with yellow pads. And to complete the entire vehicle you'll need at least 4 if not 6 of them.
Next time you'll probably be able to get away with orange pads, if not white.
May be that the Pinnacle Swirl Remover doesn't have enough cut as well. Could be you need a more aggressive pad as well as compound.
To really get a handle on what work for your vehicle it may take 2~3 different pads just for the compounding stage. Same thing for the polishing stage. Remembering that you don't want to go at it full bore, when 'half cocked' can, (and often does) provide the results you're looking for. Basically you'll need 3~4 of at least 4 if not 5 different pads.
Test spot, test spot, TEST SPOT. If you have to, make half a dozen test spots. Do one with yellow pads, speed 5, medium arm pressure slow arm speed, 3 section passes, light water spritz then 2 more passes. Then another with everything the same but now with an orange pad.
Two more test spots, except change the compound next time.
You're not looking for total correction, not at this point. You're looking for removal of swirls to a level that you are satisfied with, that works with how you use your vehicle. Plus you are still going to polish it so what little things are left you may be able to finish on down during your polishing stage.
Basically once you get it where you are comfortable at the end of your test spot, you use THAT test spot to do your polishing. From there it's just a matter of dividing the entire thing into a series of 16"~18" square 'test spots'. )
Also, there is no sense in doing a 98% correction on a daily driver that gets washed every other week. But that doesn't mean that you CAN'T, just that it may not work for your intended use. Probably a good 80% correction and you're good.

rops:
I would say do NOT get 105 and 205. Megs 101 maybe, then 205. Or over the counter you can get Ultimate Compound and Ultimate Polish which are darned near the same as 105/205. (Actually a spin off from those two, just that they work longer and have a bit less cut.) Most vehicles can be done with UC / UP twins actually.
Also, look at the Meguiar's Microfiber Correction Kit in the 5½" size. It'll give you a backing plate, 2 cutting and 2 finishing pads as well as a bottle of D300 (correction compound) and D301 (finishing polish/wax). You WILL NEED AIR though to clean them. It can be a little pancake compressor, but you WILL need it. If not, then stick to foam pads.
Once you have a couple of different compounds, and a couple different polishes as well as a decent selection of pads to work with then you just start working on your technique. The difference between acceptable correction and not is sometimes as simple as a pad change. Or a bit of arm pressure, or speed, or both. Just don't be afraid to experiment. From there it's all fun. :dblthumb2: