Without something to cut the water repellent on their feathers you won't be able to get a good scald. I've never been able to get a duck with its skin still intact... Usually they're skinned, cut up (generally the best part of the bird is the breast and legs, but the entire thing has a decent amount of meat on it), and cooked in cream of chicken soup.
I've heard that the best way to get the feathers off a duck with the skin left behind, is to pluck them when they're totally dry. I haven't yet been able to test that, but it sure doesn't work when they're wet!
I use a homemade plucker. It's basically a piece of large PVC pipe with rubber bungie cords cut and fitted to act as the "fingers." They're too long, so they kind of slap the bird, so it's back to the drawing board with that invention. It's powered by a big drill mounted onto a counter top to spin it around.