Hi!
In principle it works the same as bitmap sprites, you need different sprites (albedo/color, normal, roughness, etc), each of which will be drawn in a different pass: normals, etc. You can use Crystal_Material() or submit your own code for each pass using crystal_pass_submit(). I suspect it is possible to do this using skins in Spine? (but I believe you have to use crystal_pass_submit for this).
Thank you for purchasing, I hope you enjoy it ^^