This next step I cannot take credit for, I saw harlequin use it in his timelapse texture vid. it provides a nice amount of skin color variation. Switch over to your channels and do a render clouds once in each layer, red, green, then blue, Your result should look like this. A nice funky cloudy rainbow.

Set this layer to overlay over top of your flood fill skin layer. Then play with the contrast till it just varies your skin and not blows it into too many colors.

Check out how much just this did to your texture! So much more realistic. If you made your flood fill layer too bright previously, darken it so that when you overlay the rainbow layer it will be the correct lighting.