Ok, so many may know this but for those that don't or havn't tried it yet..
Using multiple texture maps and multiple greyscale blend maps is a great way of building up subtle textures using Projection Master rather than expecting 1 map to do all the work for you.
This obviously pertains to exporting the maps to another render app as Zbrush itself does not handle this yet in v2.
The example shown here demonstrates using a ZBrush GUV greyscale maps to blend a cylindrical projection map with a ZBrush GUV colour map.
....And obviously these greyscale Guv or Auv maps can be used to alter material properties in other apps such as specularity as well as building up far more complex examples than the simple example shown etc etc
For texture work it's cute - sort of like scratching through layers to reveal other colours and textures.
This particular example is in Carrara but the same principle applys in other software.
I'd be grateful if our beloved moderator could move this to the tutes forum perhaps under Carrara.