This is a wip, but you can see, i sculpted pores and wrinkles and applied in this case only the normal map on the model and render to see how it looks. If i am done then i create the diffuse map. In bpr renders you want to have as flat as possbile diffuse maps. You can even use a solid color if the shaders are right and have good underlying maps( bump normal sss blood maps etc). That is why you can paint a diffuse map and it still looks realistic. Of course this takes much more time then using photos. Most of time i use as a base photos and paint on them, to get rid of the things i dont like or add stuff needed for the character.