Shriek update

Hello, here are some pictures of the human character Ive been sculpting, who will eventually be fighting the creature. The first shot is of the level 2 mesh and the second is level three. After that Ive posted shots of the level 5 sculpt. Obviously I want to try and get all this info into the final shot using a displacement map, so ill try level two as the basemesh.
When I go to detail the character with skin pores, wrinkles etc, should I do this on a new layer? I will eventually try to export this detail as a bump map, but I dont want all this information to be displayed in the displacement map. I then plan to polypaint the man and make a texture map using the auv option in zbrush. Thanks for your help, Ric