Try this. I\'ve used this a few times and it comes out similar to what your after.
(using GW paint names) Colours used, Bleached Bone, Snake Bite Leather, Skull White, Yellow Ink and Chestnut Ink.
1) I base coat with Bleached Bone.
2) I make a thin wash of Snake Bite Leather. I make this wash very thin, you can see your palette thru the wash, it\'s practically dirty water.
2)a. I mop this wash over the hair, usually doing this several times depending on the consistency (how dark) my wash is. One thing to keep an eye on is how the wash is settling into the recesses of the hair. You want the pigment to settle between the hair strands to provide shading, you don\'t want it to create the dread \"ring around the tub\" effect. You might add r a smidgen of dish soap to break up the water tension so that your wash won\'t do this as much.
3) I dry brush the hair with Bleached bone
3)a. If there is too much contrast between the Wash of Snake Bite Leather and the Dry brushing of Bleached Bone, this can be corrected by making a thin wash of Bleached Bone (Just like step 2), except using Bleached bone) and applying this wash over all the hair to even out the colour contrasts.
4) Repeat step 2)a. and step 3) as needed until the desired effect is achieved. I usually end up repeating these steps 3 - 5 times. Note: step 3) when repeated is usually done lighter each time to highlight.
5) Apply a very thin Wash of Yellow ink over all the hair.
6) Very lightly dry brush with Skull white on the highest highlights.
7) Apply a very thin Wash of Chestnut Ink in areas where you want additional shading that wasn\'t provided by the Wash of Snake Bite Leather. Repeat this step as needed and where needed. Be careful to not over do it. Take frequent breaks and come back to look at the effect you\'ve gotten before deciding to do some more, it is very easy to do too much.
NOTE: the reason for so many steps and repeated steps is that if you only did each step once, it would look very stark and contrasting, Hair isn\'t like that, especially blond hair. It ranged from a dirty brown at the roots to light blond at the damaged tips for long hair. It may be platinum blond which will be mostly white with a hint of bleached bone as shading. etc. in any case the highlights very often show very subtly different colours for the highlights or shading.
Hope it helps. I think I got this from the Brush guy.