If you butcher ducks while they are fully feathered (don't have any pin feathers), you won't need the wax.
If they are covered in pin feathers, you will go crazy picking them all out. The wax takes them all off slick as can be.
You can skin if there are a lot of pin feathers, but skin on ducks in on tight and skinning them is a lot of work, too.
The shipping on the wax is high because it is heavy. But it can be filtered and reused over and over. So it is worth it if you are going to be doing ducks or geese on an ongoing basis.