[virtueco]

Could have used the Blind Skull which would have been the easiest way because you can get it in any difficulty.

Go to Outskirts in the campaign and when the level first starts walk out of the doorway and stop right away. Look up and you can see the ledges (I think they are light bars). Anyway...jump up onto the ledge and crouch jump to the top. Look left once you are up there and you'll see a little hallway type place and at the end is a skull and once you pick it up your entire HUD vanishes until you reset your XBOX.

Happy Hunting.