I think I follow (thank goodnes for batch tape loading here at the studio hehe) Once the right texture / tone is established with the grayscale maps, how is diffuse color put back in?  Through the color or blend nodes which are fed by the grayscale "color" map?

Sorry I'm not at Poser so I can't show what I'm describing in the Material Room...but I'm sure you have more details coming Cath.