Angel wing hits most of the time only one side, but it can hit both. You can get the vet wrap at the vet or the feed store in the horse isle. It's about 2 dollars a roll, which will cover about 3 days. First wrap the one wing once and then wrap it around the body twice starting off near the legs and go once higher. You will need to get the right tension so the duck does not get out of it, and you will need a helper wrapping the duck. You will get the hang of it really fast. It is important to wrap the wing first in folded up position or the duck may stretch out the wing under the wrap wasting your time. Please take the wrap off at night so the duck can stretch its wings and get the blood circulation going. I think you will be fine after doing this for 3 days. Angel wing is more a cosmetic thing, but a wing hanging out can be prone for accidents to happen. I feel it is best to treat it early. You duck may never fly, if it is a flying breed, even with treatment.
Almost forgot, pick a dull color like dark green or purple. Some bright colors may frighten the other ducks.