Realize that this isn't advice coming from Joe Blow. I do this kind of stuff big time. There are many more routes to be taken before an acid wash would be warranted. When detailing, you always want to go the least aggressive to the most aggressive. The acid wash is just shy of a wet sand so let's try something else.
I agree with you. I'm just saying if he tries everything and it doesn't work, acid bath/sand blast is the final step. I had to have my rear bumper sand blasted because of some crazy water spots . I tried everything and the only thing that worked was sandblasting heh
I agree with the clay bar. My old man took his '05 mineral grey into a body shop and they used vinegar on the roof and then polished it right away. It looks great now.