applying more than one multishader to a model

[daringd 2]

So,

after following Mandkalb's multishader tutorial I have figured out how that all works and how to apply it to my models, though now I am trying to work out if I can apply more than one multishader to a single model.

all of my internals, floors, walls and so on have one rvmat, and there are not enough textures to go around, so I thought of adding and 'external' rvmat to deal with all of the external texturing, brick work, plaster and so on, but so far I can't quite get it to work, I've spent a couple of nights trying to muddle through on my own but with no success.

I suspect there is something simple I am not doing that wil be the magic bullet, but I can't figure it out

I looked over how the BIS pub is working (the corner one with the beer pumps) and it appears to have several rvmats and masks for internal and external texturing, this is what lead to my own idea of doing it too, but I'm just hitting this problem.

so far I have UV set 0 laid out to scale all of the overlaid textures and normal maps, and UV set 1 laying out all of my CO work, and this works perfectly for all of my internal modelling. I tried to follow the same process while modelling all of my external work (roof, outer walls and so on) but it only shows up as black, no colour, no normal maps, nothing.

so far the internel and external sections are not connected to each other so they are essentially separate objects.

if you need to know any more to be able to advise me, then I will get the info you need.... I'm so close!

D