The first thing that struck me about that photo is how assymetrical his face is .. the hairline lifts up a tad on the right, as does his eyebrow. Might be expression, might be the angle ..but it looks good :) For the hair ..sample a medium tone. Than make two layers..on one paint pure white for highlights, and use a heavy smudge to mush it aruond and make streaks. Set that layer to screen. Turn it off, and on the second layer do the same thing in black. Set that layer to multiply. Now turn both layers on and adjust the opacities until it looks about right. This way you can adjust the base colour without bothering the lights and darks. Hope that helps!