Very nice work!
Though Id try and slightly erase randomly on the rivets. It gives them a worn look. As of now they are too defined IMO.
Those dark circles are actually holes in the aircraft that go through it.
Check this out. You can see it here.
I very much like the worn, dirty look to it as well.
But, I think I'm going to have to go against my opinions and say this: The Navy kept their birds clean because of all the salt getting into the plane. Im not so sure, but Ive seen that they wiped up all of their planes regularly, but dont quote me on that.
