First off I want to explain to you that this is that bug where hunters crit people for 2 billion.. you can bascially take any class
and dual wield any 1 handed or 2 handed weapon.. or even wield 19 staves at one time!
So to begin.. you first get a Spellfire Bag from your server's bag vendor..
you then put it in the far LEFT side of your bag equips...
Then, choose the vendor that has the item you want to equip, and drag the item over to the spellfire bag *note you have to be naked, and it also has
to be dragged, not right clicked*..
How you know if its in the right place?
Well.. its basically like coordinates.. 1x2 is the neck piece slot *1 being the horizontal row and 2 being the vertical*.. the others you can just start guessing
EDIT: People say it does work with any other bag, but I have not tested it yet.