Noodled a study into oblivion-jks still conscious of the process, here I composited the different light sources (bounces and sub surfaces scattering)

My main focus here was handling exposure efficiently and image 3 is a good example of what I should refrain from doing which was just applying a multiply layer with the desired light source color to one (under white light). You can see the light side on 3 lacks some sort of realism or maybe it just lacks punch and contrast when you compare it to 1 and 2.

Quite pleased with 2 (which was the intended result achieved through compositing) though it has a better read and I will be applying this technique to future pieces (I have already been applying it :p) I think all else is self explanatory and not much else to be said here.

Tl;dr Multiply layers if not combined with other modes efficiently will play against you and if force you to rely to cheap tricks (color degrading use of levels) to achieve a believable result.
Again all this should be taken with a grain of salt because it all depends on what you are aiming for.