I have never polished before and plan on using OP and OC for the first time on my 05 Lincoln ls, how do I know when they are broken down using the PC? Also do I use different pressure when polishing to remove swrils than when I'm trying to finish lsp?

In my experience you will be working OP or OC a long long time with a DA style polisher. Important to break both down for best results but I would say more important with the polish since its the last step. Product requires heat to break down so combination of speed and pressure required to get that result. You will know when you have broken down the polish when it becomes translucent on the panel. More or less disappears and becomes clear. Dusting not an issue so don't judge by that. With a DA I would say at least 3 minutes for a 2 by 2 area at full speed. Look for the change in color and you will be fine. Good luck,

Pat.