Adding surface characteristics

Is there a way to add characteristics to the "surfaces" tab of a pre existing material/shader? In the case in point, I want to add an additional surfaces characteristic (in this case I want to be able to add a top coat bump map) where there is not one present in the surface of the purchased model. Other top coat sliders and maps are present, but I want to add a top coat bump (in this case for perspiration) where there is not currently no image box.
Comments
I thought you need the Shadermixer/builder [?] for that. At least a few use it on this forum I believe, never really used it myself. It should be an item in the Daz menu I think.
you don't have this?
That is the default DAZ material, which (I'm pretty sure) is the same as "Shader Presets\Iray\DAZ Uber\!Iray Uber Base" but your model may have a different shader/material setup - you can just change the surface to use a different material and transfer the relevant settings like color map or bump map or whatever.
Thanks, I'll have a look.