Depending on how much bone you're painting, and the effect you want, there are a couple of ways. Valar's style , and Reikai's are both clean, while Ian's looks a bit more anchent.
Personally, i use a combination of techniques based on what i'm painting. For generic, rank and file (Catapults, tank engines, chainswords) i use a simplified version of what Reikai does. Dhenb Stone, followed by two(2) washes of Griphionne Sepia (to create depth) and a drybrush of Bleached Bone. Substitute look alike colours where appropriate depending on your brand.
For more prominant figures, such as Autarch weapons, Banshees, and Farseers, i put more effort into it, working more like Ian. I start with Snakebite Leader, then Rotting Flesh, Bleached Bone, wash it in Griphionne Sepia, highlight with Bleached Bone again, then do fine Skull White highlights. If i want it to look more ancient, i'll either not do the second Bleached bone, or use more washes.
With the first, i can throw out 20 Shruiken Catapults in about 30 minutes (including drying time for the washes) and the underside of a tank in 10-15. With the other, it takes be 30ish minutes just to do the rune armour on a single Farseer.