Whelp, after 4½ hours of fiddling with Unity and Blender and trying to follow guides, I've come at a standstill where the Model doesn't wanna let itself have the textures from the created atlas, it just puts everything in as opaque, not the transparent thing you see in the tupper guide - I think I did something wrong at some point in blender and I feel too defeated to restart from the begining. Next time I'll try a simpler model to go on, but I was happy to find that stuff like mouth and eye tracking was really easy to set up, and that merging bones weren't all that complicated either. Hopefully I'll get something going soon.