Here's some things I'd share:
Be gentle to the headlights and never aggressively spray them with a pressure washer. Learned this after my headlights showed bubbles after washing:
Use the lightest polishing step you can when machine polishing. I hired a detailer once and he used a medium cut polish, which cleaned the car well but it took down a lot of clear coat. The BRZ's factory clear coat is what gives the car its luster and without it, it doesn't look as great. The clear coat is very soft and can be cut down very easily with too aggressive of a polishing step. If I were to go back I would have used the right pads and polishes. Notably, lake country finishing pads and M205 would probably be the most I'd use.