Im not very experienced with airbrushing blacks infact apart from priming i dont know if ive done any. I am looking at doing some 30k style dark angels one day for a small fallen squad and Cypher and i stumbled across this video that may be of use.
This is quite a nice way of doing it. Basically black undercoat and then white grey highlights. Then applying a dark glaze over the top to blend it!
There are other ways of doing things tho. I've recently tried applying gw shades through the airbrush as a post shade to try and darken shadow areas which is quite a nice easy way to do things.
@pawl seen any good vids youve seen?
There is also my man... MAD DOG KENNY BOUCHER! Who Pawl cant stand but i now love
He gets great results but his techniques are achievable. Not sure if hes done raven guard but im sure there will be something similar.