Hacks - Putting a certain model on a character despite class?

[Supercredit]

So yes i have cfw and all that jazz. Im curious as to how I can put a specific model on a specific character despite class. Ive seen it done before but its never explained. An example would be Keeping Rinkahs original body on a promoted class shes in.

 

Or keeping Camilla in her original outfit despite being an unmounted class. Or lets say, Giving Arete's body model to one of my characters. 

Any help would be great. 

[Re: The weirdo.]

i don't know much about this whole hacking thing, but you could try labelling a copy of the model as to be set for the class you want to change it into? i dunno, that seems like it might work, but im talking out my ass, so if it works, well wow, but it probably won't.