As most people are transferring multiple puzzles at a time, it became important to make the process easier.
If you want to transfer multiple puzzles to someone quickly, simply look at the details for any one puzzle that you want to transfer, scroll to the bottom and click the TRANSFER button. On the transfer page you will see a new button marked TRANSFER OTHERS. If you click this button, a new screen will appear letting you pick multiple puzzles to transfer at one time.
When it comes time to ship (or hand deliver) the puzzles, just follow the normal process. When you start to ship a puzzle (or hand deliver), you will be shown a list of all open transactions with that same person. You can pick all the puzzles in that one shipment and mark them all shipped using the same method and tracking all at once. If you did an in person trade, just pick HAND DELIVERED as the shipping method.
Hopefully, this will make transferring multiple puzzles to one other person all in one shot a lot easier.