For example in this image I used the alpha "brush 22" to create some veins on the nose.
Now leave the "PM" turning on only colour and fade. Fix any eventual parts where the texture doesn't look right, drawing the colour directly onto the model with the standard draw pointer, with only RGB turned on.
To do the shadow of the beard enter the "PM" and, as in the next image, select the simple brush with alpha "brush 40" and "spray stroke" with a dark grey/green hue. Paint the shadow in the appropriate areas. Do the same thing on the other side.
Leave the "PM" with only colour and fade turned on and take a look at the result.
Now go to the texture menu, flip the map and export with the format you prefer (I use TIFF).
Create another texture map, again at the highest resolution; this will be the normal map. To do this I use a plug-in called Zmapper that you can find on the Pixologic website.