Surveyors marking tape works great.
The same stuff we use to mark blinds.
Hold the wings together and wrap the tape around the base of the wings five or six times and tie off.
Even the beak. Duck hissing can be intimidating to a shy or young dog.
The tape has no stick-um. It is soft and tears off easily.
Removing the tape is necessary if you want to save the duck for another training session.
The big killer. The duck isn't able to beat it's wings and soften the landing if you throw the duck as a mark.
Pulling flight feathers instead of shackling allows some softness to the landing if you want a live flapping mark you can throw again and again. Tying the feet allows you to throw the duck as a memory mark without it walking away from the area of the fall.
It depends on what you want to use them for. If you use them in the water, they will use their wings to swim, and dive. So I use a large, wide rubberband on their legs, and a nylon ( like pantyhose) strip to tie around the base of the wings. It should be tight enough so they can't fly. If I use shackled ducks on land, I tie their feet with a rubber band, and clip the flight feathers ( about 1/2 way down the feather) on one wing only. If you tie up their wings and throw them on land, they often end up with internal damage. and die. They need some wing flap to keep from hitting the ground hard enough to do internal damage.
If you want them to fly naturally wrap their head with vet wrap coverering their eyes. Make sure you don't cover their nostrils. When you throw them or kick them out of a winger they will flap but come down quickly but softly and just sit there. May have to reinforce vetwrap with duct tape since they will try to scratch it off. End of day just take siccors and cut tape off. This also works well if you have a bad shot for your gunner on a flyer. Bird flaps naturally, if they miss you don't lose duck.