I had the same problem this past summer. I bought a brand new Mercedes Benz ML350 in Diamond White (paid an extra $1500 for this beautiful paint). I've been driving cars for 50 years and have been washing and waxing for longer than that so you can imagine I have a lot of experience - by hand. Since I've detailed all those cars by hand I decided to get a Griot 6" polisher for the Mercedes and really do it right. When it arrived and turned it on I said to myself this thing is a beast - no way does it get near that Mercedes!!
I use Duragloss products for the most part and had a lot of success with my Silver Honda Ridgeline just doing it by hand but after a day of working on it my hands and joints would get tired and sore. They just are not as strong as they once were. So, I decided to take the Griot out once more and practice. I used it on the Ridgeline, the shower stall, a friends old Sonata, my hot tub interior, range and counter tops, etc. If it needing cleaning or buffing I would reach for the Griot.
I found it was not a beast after all. It was easy to control and I was able to get the hang of it rather quickly. The jobs seemed a little better than by hand but certainly a lot quicker. I decided it was time to do the Merc. I had Griot pads and also some smaller Uber pads. I used my Duragloss 601/105 combo and since then also the 601/111 combo. Both times I was impressed by my polishing performance and the outcome. I was able to spread the products very thinly, almost transparant, which is important. The final buff to shine was no trouble whatsoever because of how thin I could apply the sealants by machine. I was never fully able to control this by hand but now I can.
I think the lesson here is that the only way you will be comfortable is to practice. Detailers use these machines every day but we only take them out a couple times a year. You can't get familar enough with that kind of limited use to have the confidence to work on a car, especially a new and expensive one. But if you find ways to just get it in your hand and work with it on older cars, shower stalls and all those other things I mentioned, you will get the feel for the polisher quickly and easily. You will then wonder how you ever detailed cars without a polisher before. Good luck!