I cleaned my shower a few months ago. I tried various products with my UDM: PB Pro Polish, DP Glass Polish, and A-MAZ (ned to google but was a recommendation from a windshield replacement place).
A-MAZ worked best by machine but it was very finicky. It was a thick paste and I had to clean the pad after each section. It clogged the pad as you would think. I used an orange 4in
CCS pad, and lots of pressure, with lots of A-MAZ -- less is not better. I was able to duplicate it by hand with significant pressure but again a fresh pad or applicator was key to remove aged water spots.