Not to hijack the thread, but I'm in the same boat as john1c where we have the same car and the same polishes.
Just over this past weekend, I tried out my new PC on my roommate's BMW with OP and I had difficulty in determining whether the polish had flashed. Since OP has a long work-in time and practically no dusting, how can a beginner know when it's done? I watched some of the videos that are around here on polishing and it seemed pretty obvious when the polish was broken down, but on the BMW (silver paint), the polish looked the same from start to finish. I almost think that I should've gotten PB's SSR so that it would dust and give me an indication that I've worked it too long.
Any advice would be most appreciated. I'm sure this might be useful to john1c as well.