How to:
1) Have a weapon.
2) Get 1 placeholding weapon of the same type of the weapon you want to transmog into.
3) Place your main weapon in the bag and in the hotkey bar, for the faster swap later.
4) Equip the placeholder weapon in the main-hand.
5) Put desired transmog on the placeholder weapon.
6) Press "Apply" and instantly the hotkey to equip the main weapon.
Works with every weapon you can equip, for example rogue can't transmog 2H weapons because they can't equip it, but can do dagger into sword or vice versa. This bug existed in retail and will exist in most (if not all) private servers that have the same transmog system.
![](https://i.ytimg.com/vi/4Lmt9iABgCI/maxresdefault.jpg)