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.
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. 