@Oh_Man
I will try, guide will be using GW paints and will use one of the large horns as the part being painted.
Base coat Zandri dust when dry apply an agrax shade to the whole area, when dry apply Ushabti bone start at the tip and work down the horn and stop about 3/4 of the way down, when you stop create a zigzag pattern to help the blend, try to keep the paint thin.
Now take screaming skull and apply from the tip to about 1/2 way down the horn again do a zigzag pattern but thin the edge where it meets the Ushabti bone, wet clean brush works well, might need 2 coats.
Apply a spot of skull white on the tip of the horn.
Where the horn meets the flesh apply a thin line of rhinox hide, thin this down slightly, then apply thin lines from the base of the horn with rhinox hide going up the horn, small lines are all that is needed, you want to see the Ushabti bone.
Does that make sense?
I've got a Steggy to paint so I could do a tutorial for this if needed.