My texturing process goes like this. First I fill the model with the basic color and then do a rough polypaint (all in ZBrush), not caring about the resolution or the details a lot and just finding the right color scheme for the creature.
From time to time I export the texture as a low res PSD file and render it in Max, then paint more to try and get the look I want – I find this approach gives me the best and most predictable results.
When I’m more or less happy with the result I export it as a 4k texture, open it in Photoshop and apply hue/saturation to correct the color, curves and to raise up the contrast. Then I apply this fixed texture to the model in ZBrush and start painting on it using projection master – now working on fine details. I often mask the model by cavity and brighten or darken the details I need. From time to time I also open the texture in Photoshop and add extra textures using different overlay modes. These layers are often only 10% visible but I find they add the needed vibrancy and variety. The standard color evolution looks something like this (Fig.06).