Hi FinalBossLeo, the technique and the shader is explained in this thread: Unity-Sprite-Lamp-BumpMapped-Spine-texture-regions-2138?p=17252
As far as I know my implementation is outdated, I'm actually deeply immersed in other projects that do not use Spine, so I can't dedicate time to that project again. But you are not the only one asking me about it, maybe I can dedicate some time in the future to update the implementation for the last Spine Runtime and Unity 5