So I watched the Bone Effects FB live demonstrated by Ashley of Powertex Australia.
Followed the steps, added the bister, wiped back...
Added more ivory, wiped back added more ivory, more bister and wiped back.
Added some head gear.
Decided to add red eyes.
Didn't like the red, so painted over them in white but added more red around the eyes.
Added a light inside the skull. This was taken in total darkness with no lights, just the camera and tea light.
And this one was taken with the main light slightly on.