Skeleton Horde over Wraithbone is what I've tried (for exposed bone).
It does give a very nice (quick and easy!) effect BUT more of an aged, exposed to the elements, yellowed appearance.
I would suggest dry brushing, gently and lightly, white to bring the figures back to a newer state.
Bones out of the ground are very white as they have been stripped clean by insects.
Out of a coffin, is more yellowed:
YouTube link
There is plaguebearer flesh. A grey could work, as well, as mentioned. I guess it all depends upon how long the corpse has been dead and decomposing. I'd suggest a quick look at skin tones for pathology.
I'd mix and match and mix the Contrast paints with matte medium (Contrast Medium) and try various base coat tones (ie Corax White, Grey Seer, Wraithbone, Tamiya white, Mr Hobby white, etc). No two zombies need be identical in shade and tone, just like no two living humans are identical in shade and tone.
Have some fun and let us know with some pictures!
Remember, if it doesn't work the way you like, reprime and try again.
One of the beautiful things about Contrast paints, I've noted, is they go on very thin so they do not distort details (unlike base coating in black and then putting on layer after layer of paints).
