For the metal, I drybrush with Tinny Tin from Vallejo (Tin Bitz if you're using
GW), then I drybrush lightly over it with Gunmetal Metal (same as Boltgun Metal). Gives a nice contrast and makes the metal not look as flat.
For the flesh I use Sombre Grey (same as Shadow Grey from
GW) as basecoat, then a 1:1 mix of thinned flow aid (mixed 20 parts water, 1 part flow aid) and Wolf Grey (Space Wolves Grey from
GW) for a smooth consistency. After that, I mix in Bone White (so the mix is 1:1:1, if you may) for rough highlights and at last add another 1 part Bone White to the mix (so it's 1:1:2) for tiny highlights. Can barely see them on the pics, but they're there.

Hope that helps some.