I have both, an old bottle and a new, i've used both, i prefer to spray everything, APART from Klear, wide flat brush, quick swipe over the surface, I guarantee I could cover a large model faster than anyone on here could airbrush it, it self levels as it's water thin, any runs and streaks are quickly sorted by blotting with the dried bristles, a piece of kitchen towel or if dried, recoating with more Klear, it dissolves in itself.
For the record, again, the new and old stuff, despite the new being opaque and milky, behaves in exactly the same manner with no difference whatsoever other than the smell which is a more perfumed odour in the new one
Two to three coats WILL give a glossy finish, you will not get a mirror deep shine over matte paint, regardless, if a couple of sprayed coats isn't glossy it's not laid on thickly enough, problem with it being it's water thin is it's all too easy to create runs.