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I would do the scars this way:
I would leave the scars and the shadows off the image completly and treat them like they are not there.
Then I would do the flesh tones and gradients in the flesh.
I would then do the scars on top of the flesh, I would do them all in one color and then duplicate the scars and apply a slight blur to the scars to diffuse them a little.
Then I would do the shadows above the flesh and the scar's change the opacity and blend modes till it looked correct (You probably need a gradient in there as well some how).
If you want the slight texture thats in the image I might try adding that to the scar only, to do that you do it the same way as the shadow only you just make a copy of the scars and apply the texture.
The image is a quick break down of the layers and how I would do it, its up to you however.
Good luck!