This is what we have so far, but we're not done yet. Just one more step to complete the effect. I hope you're still with me. :)

When you look at real hair, the highlights doesn't look this smooth. The last thing we're going to do is simulate the texture of hair by using the Smudge Tool .

Set you Smudge Tool to fairly sized Soft Round Brush, Mode to Normal, with Strength set to about 60 - 70%.

Start by just smudging the highlighted area using a zigzag stroke.

Now this part is mainly experimenting and trial and error on your part, adjusting the strength of the brush to your desired effect.

Don't be afraid to use the History Palette in Photoshop if you're not satisfied with the result