You will do well with one pass, especially with black.
With mine, it was kept under a car cover for 3 years and the microscratches a swirls were a huge pain, the paint is super hard too.
I used ultimate compound first to get to a suitable finish but I did quite a few passes as the paint was just so hard. TBH a more abrasive compound would have been better but im not a pro and UC is meant to get you most of the way there. Polished to buff the gloss back into it, then sealed it.
TBH it was so bad and you need to invest the time, I did mine in May and had late nights but it took me the best part of a week.
If the paint isnt too bad then it can be achieved quicker. Night and day after id done it.
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