Hey guys, not saying I am the founder of this or anything since I got the idea from someone else's tutorial(Getting to the last boss of UBRS).
So you will need Noggenfogger Elixir - Item - World of Warcraft. Position your mount under a barrier/wall you want to go through after obtaining the size buff from the elixir. Unclick the buff and log out. Once you return to the game you will be able to fly upwards and through the barrier.This works with most if not all barriers/walls.
Note: You don't need a mount to do this, just makes it a lot easier.
Should look like this when you are positioned correctly and ready to unclick the buff.
http://i.gyazo.com/116727fa74322a9de69d927410580a88.png