use kratisto's decompiler on the original esf aura (its included with the latest version of milkshape if you have it)
look at its qc file for the code you need to add multiple skins, i dont know it off of the top of my head
kratistos decompiler will show you the original qc file, as opposed to generating a new one for you. so you can see all the lil goodies that the default decompiler wouldve normally missed