Not sure what the answer is, but I have the same problem to an extent. About the only thing I can use is a product like Sellys Stone Benchtop Cleaner, which I have to use when the top is completely dry. Then after that dries up, I have to buff it off with another clean dry cloth. It's still not like it looks in the showroom, but it's better than using water as they suggested when it was installed! I don't know if it makes a difference that our top is the Night Sky colour (mostly black) as I would guess this shows up the streaks more.
I'd be interested to find out if there was something better. And by the way, Metho doesn't get it looking any better either, contrary to some suggestions...........