Don't use nova skin shaders or parts this can result in PMC ban if you post a skin using this technique! I would use gimp or photoshop to do a light brush at the center of every side then use a dark brush near the edges. I personally make a skin pixel by pixel and for each part i use 3 shades. i put those depending shades depending on where i want the shadows. Then i use the smudge tool to make it a smooth shading then i use the brush tool over that for finishing touches. I hope this helps.