I agree that your comment was rather brusque!
In any event, as a native speaker of English I would say that either order for the adjectives is fine, depending on context. If I had two fast cars and I wanted to say that the one I purchased just last week still has wet paint on it (whereas the one I bought last year is ready to drive now), duo's sentence would give the correct emphasis. Not particularly elegant, but not in any way wrong.
Nope, nothing wrong, actually, I would say it sounds more reasonable to me than "a gyors új autó". That lowkey sounds like you had multiple new cars and you make a selection saying that you mean the fast one among them. Or, possibly it sounds like being new was a more inherent trait of a car than being fast.
This is about a fresh paint job?
I understood "not dry" as it "leaks oil". In the sense of "I bought a new sportscar but the damn thing loses oil!".
Is it possible to say "not dry" in that sense? In Hungarian and or English?
I would assume just wet after a car wash might be more reasonable than a still wet paint job?