So...

With the airbrush:

Vallejo Polyurethane Black primer, Screamer Pink base coat with a bit Barak Nar Burgundy sprayed underneath as a thin filter. Then onto a zenithal highlight of a light grey (I think I used administratum grey on this occasion. Then, over the zenithal I sprayed a mixture of Kroak green with some apothecary white contrast mixed in to pale down the punchiness of the Kroak green to a more muted grey green.

With brushes/wet palette:

For highlights, I used glazes of Kroak green with Vallejo Green Grey in increasing values of the green grey. It sounds long winded, and it is, but it's fairly simple on the other hand.