[1.8] Rendering a different model on the player

[HappyKiller1O1]

So, I was following a tutorial on adding some custom models to a mod, but it was for 1.7.10. With this, ItemArmor#getArmorModel() was used to get the actual model. Sadly, this method is gone from 1.8. I read that 1.8 uses layers for models being rendered on the player, but I'm not sure where to find the place to render these. If anyone could help, I would be very appreciative! 

[HappyKiller1O1]

Actually, found getArmorModel within the Item class. My problem is, I am trying to render a custom model (backpack) on the players back. I made the model, set the class, and made my base model of it as a child for the ModelBiped body. But, how would I go about rendering this on the player when my item is in my custom slot? I feel like I should do this in #setInventorySlotContents, as to not constantly be checking for it in a tick handler. Still, I have no clue how to render things like this in 1.8.

[HappyKiller1O1]

So, looking into it more I found the class that renders armor. Except, the methods are all "func_..." which is quite annoying. Perhaps someone could explain how I would go about using that class, or how it renders things on the player, to allow me to render my custom model on the player?