Let's say I add mi_car_paint_phen_x and mib_amb_occlusion to a layeredTexture. (did you mean layeredShader?) Then I need to connect the layeredTexture to a material, I can't just assign the layeredTexture to an object. Non-mentalray materials don't play well with mentalray materials so putting the layeredTexture in the color slot of a blinn probably wouldn't be a good idea. If I put the layeredTexture in the color slot of a mia_material_x then I might as well enable the ambient over there and not bother with layeredTexture and plug the mi_car_paint_phen_x in the additional color slot of mia_material_x. That's what I did and after spending time playing with the settings I got both the ambient and mi_car_paint_phen_x to show in the render. The ambient looks ok but I don't think mi_car_paint_phen_x shows too well. ¯\_(ツ)_/¯