That has always been a problem with no easy solution.  IIRC, there might be a script to make those isolated changes over selected object parts.  Currently, I use bagginsbill's VSSProp to enhance the skin textures of all my models.  The convenience, one change will carry over to all associated body parts.  Very easy to use once you get over the small learning curve, and you won't deal with unnecessary skin tinting unless you desire it.  Search the forum for VSS.  It is a shader system that make a world of difference.