That's not an airbrush, that's layers of highlights
Ok break this down for me. I see: 1. Black undercoat 2.Medium blue armor panels/helm, in what looks like straight over the black undercoat? 3....
https://www.eccentricminiatures.com/retems0002.html My secret source for great helms, that and historicals.
Contrast paint is essentially a heavily pigmented wash. Dark angels green is almost a black-green, or a very deep Hunter green.
When I was 19-20, had no life and an endless supply of caffeine, I painted 120 models in a weekend. They were meh, and honestly looking back kind...