I've setup the lights selected the object and in the convert texture options selected bake shadows this time.
Here's the baked texture image, using this in your photoshop file can make Painting easier instead of using the Uv map to paint different layers.
You can actually use some baked textures like this in your maps, its not really any use in a bump map , but can be useful for spec or diffuse map for example.
Here's my bump map so far, you can see how i've blended in the baked texture for now, its makes it easier to paint.
A test render.
I've added more layers and more wrinkles the photoshop file can start getting quite big, you could start merging some of the layers to together to reduce size. But its best to keep as many open as possible because there's always some tweaking to be done later on.
Also in the above picture notice after painting the wrinkles on one side i've copied and flipped them over to the other side, saving time.
Here's the bump map almost finished, its not actually very good, but it will do, it was rather rushed.
You can probably see parts of the different maya texture maps I used, its a quick way of making half decent textures.
It would have been nice to of been able to of used some displacement, it would really suited a head like this.
That's the bump map kind of finished, I might go back and tweak it some more later. Now its on to the colour map.
Like the bump map it can be hard making a start on the colour map.
Well lets start with just a skin tone its R227 G183 B156 if you can't see the number.
Then on another layer a slightly darker tone R217 G157 B137.
Next I have diffused the darker skin tone layer then added blur to it, to get a nice variation in the skin texture.
That's probably the key with skin the variation in the skin tones.
More 3D Graphics: 
