Usually texturing the head is a slow process and it keeps until the final image is rendered.    For this project  I've used many references to get the proper position for hairline, eyebrows (extremely important) and wrinkles.  Almost every personal work is a researching  process and here I've tried to get some pore details to be visible on the skin . So I've done lots of test to see how i can make some nice pores on the diffuse texture but also on the bump map.  These days I'm not using anymore the bump map created in photoshop with this method but I'm using the displacement map from zbrush to create the pore details in bump and diffuse. Anyway .. here's how I've created the texture : Usually I'm creating the uv layout while the model is still simetrical , to make things a bit easier for me. Because the base head was symmetrical the uv will be the same. So I'll use just half of the head to create the uv . For this I'm using an cylindrical uv and I'm correcting the points that are overlapping and the uv starts to look like this :  after that I'll mirror the other half of the uv and merge together in a single piece.

At this point i can collapse the whole stack and the uv information is stored in the base mesh.
After tweaking the geometry by adding the proper asymmetry on the model face i can start painting the texture in photoshop.
(At any stage from this point if i want to add more details in the geometry i have to apply again the unwrap modifier and to correct the area where details were added.)
First of all I'm painting some guidelines for eyebrows and forehead and I'm creating few noise layers with different level of blur (all with an overlay transfer) and an layer base color for skin.Here you can see some steps for the skin pore details :
 To add pores details on this basic texture i fill an layer with black color and after that I'm reducing opacity at  4 %  . This layer should have an dissolve transfer and the image will looks like this :
After that I'm creating a new empty layer and i merge both layers ( the one with dissolve and the other empty one). In this way i have a new layer with a normal transfer.
With an emboss effect on this layer and overlay transfer i got exactly what i wanted .. pore details :) and as you can see in the grey area of the image, the same layer I've used to create the fine pore bump map.
With some guides for eyebrows, hair line, beard and wrinkles painted on top and with more color variation I've started to analyze again the references and to properly arrange all details on the face.