Hey dude,
We've not spoke for a while, nice job so far !
I recently finished the japanese dive bomber pilo bust.
Hiis goggles where also up and where tinted blue.
With acrylics I painted navy blue and german grey black overall,
then gloss varnish, then washes of lighter blue-tinted gloss varnish till I was happy.
You would get the same with your oils first a blue-black centre fading to grey black at the edges,
And then gloss varnish over I would think.
If you wanted to see the helmet behind through the lenses, I would paint the whole helmet, then use that smoke arylic over to darken slightlly and then gloss varnish the whole lens area a couple of layers.
I want to see this completed it's a lovely piece.
Take care
Paul.