They are awkward. Have your story ready to go. Why are you wiring $20 to someone in another country? And why a few minutes later do you need that $20 back? The WU reps are looking for fraud, so just try to look as normal as possible when presenting this unusual scenario.
Beyond that, the receipts are very long, so be prepared to cut them up and place them next to each other for photographs. I usually lay mine out on the floor.
Good luck!