Something I'm really liking about Necrons is that I can try out lots of airbrushing techniques and really bring units quickly from Grey to painted. I took a night and painted up my Annihilation barge, 100% with my airbrush. I started with Badger's Stynylrez Gray Primer. This was the first time I'd used it, and I like the idea of using the grey primer, but it's definitely a little odd to use on grey plastic, hard to see where has been sprayed. That said, the primer was very forgiving and leveling on a couple places I oversprayed.
After the primer, it was a quick series of paints in my brown/bone scheme. First coat was Minitaire Muddy Brown on the entire model. This was followed by a ~60 degree highlight with Minitaire Bark. Finally, a nearly completely overhead zenthial highlight of Minitaire Ancient Bone.
After the base color was down, I used white airbrushing on energy areas and guns in preparation for blue OSL. I then went back over these areas with Minitaire's Plasma Fluid Ghost Tint. Finally, I added some white/Plasma Fluid mix to highlight some of that direct OSL.
In all, I painted the entire Annihilation Barge (and the associated Overlord) in about two hours, start to finish. Yes, it's a quick paint job, and could use some details and cleanup, but I'm pretty happy with it.
Some thoughts about additions would be whether I want to extend the blue effects to any of the dividing lines or symbols on the wings and spine. What do you think, does it need more, or would that be too much?
*Update - Thanks to everyone's advice, I went back and added some brown and blue washes in some recessed areas: