The vast, vast majority of the parts I've used over the course of this project have come from the Dwarven Sphere model. There's two very good reasons for this. The first is that it's simply built differently from the other Dwarven enemies, with almost every individual part of its character asset model a separate and distinct mesh where the others have their components merged together, which obviously makes the Sphere parts much simpler to use. The second is that the Sphere parts are usable right out of the box. They work properly in Outfit Studio and show up properly in-game without you having to jump through any hoops. And for the longest time, I didn't know where those hoops were. I simply couldn't get the Vanilla Spider and Centurion parts to work. 

Well, I've figured out the hoops. 

They are very obnoxious hoops, involving manually resetting the textures and using OS to generate a working .nif, but eventually, it works. And the parts being merged actually helps a bit, since it means you don't have to do the texture step nearly as many times. 

But how do you get something usable out of a big pile of fused components? 

Well, I've gotten a lot more practice at selectively masking things off over the last few weeks...