Its quiet impressive and looks easy to create, moreover, you have described what u did in a better way than writing a long tutorial...It's been a while since i posted something but i've been very busy studying.
This is an interior study with mental ray. Only two lights in the scene, one keylight (pointlight with mr area sphere) and one fill light ( to brighten the effect ). All materials have dgs and dgsphoton materials attached to them. only 50000 photons and 200 fg rays. All the materials have the mix20layer mr node attached so that i could mix in the dirtmap shader.
Like to know what you think of it.