I find this topic interesting as I've often wondered what I'd do if I were somehow unable to detail our vehicles
I dunno...correcting paint is something you don't want botched up and I wouldn't want somebody learning on *my* vehicle; so telling somebody to use unfamiliar abrasive products sounds risky. But if somebody said there were gonna correct my S8 with something I'd never heard of (or had a low opinion of), I'd sure think twice about letting them do it.
So I can see this from both sides...but it's not like
Menzerna is some snake oil product. I don't use it, but if somebody who's familiar with it wanted to use it on my vehicles I wouldn't really have a good argument why they oughta use my beloved 3M/1Z stuff instead and I'd be forcing them to ride a whole new learning curve- on *my* paint.
When
ebpcivicsi did my Denali XL (long story why), he used compounds and polishes that I don't use (Meg's and Menzerna). OK by me for the above reasons. I did have him do a 845/476S LSP job, and he ended up loving the stuff and adding it to his arsenal. So he and I were able to find a middle ground that worked out for both of us. If the pro and the (opinionated/knowledgeable) customer can't come to an agreement like that, it wouldn't surprise me if one or both ended up unhappy.