Working on Arc Emu r 450 (Tested it myself)
It is some what similar to the other guide but easily readable.
Things you need:
-2 people (of course)
-A travelers backpack (works best, other nonsoulbound bags work)
-The items
-The one who will be giving items needs a hearthstone.
Things you may not want:
-One partner going to snitch
-An addon that makes your bags into one huge bag such as OneBag.
Now for the method:
-Both players need to make sure the bag slot next to their backpack is empty (meaning you have backpack, empty, other bags).
-Once there is an empty spot next to the backpack...equip the nonsoulbound bag; both players must do it.
-Both players open up that newly equipped bag.
-The person who will be giving the soulbound items should: Drag the bag that he equipped onto the other players portrait. This will open up the trade window.
-When the bag is open, go to the bag in which you have your hearthstone in and place the hearthstone in the tradable bag.
****THE HEARTHSTONE HAS TO BE IN THE UPPER LEFT SLOT OF THE NEW TRADE BAG****
-Once the hearthstone is in, the giver hits trade and the receiver hits trade afterwards.
-MAKE SURE TO NOT CLOSE THE BAG
-Now drag items and drop it in the slots....MAKE SURE TO NOT STACK OR PLACE ITEMS ON EACH OTHER.
-Now you should see the items drop in but disappear. This states taht you are doing it correct.
-Once the items have been traded, the person who was giving the items must logout first, then the receiver must logout.
The new items should be in the 2nd bag slot (the slot that you cleared then put in a new bag).
You may be wondering...wtf where is my hearthstone, just go to an innkeeper and make that your home.