I have zero experience with Muscovies but I hav read: (1) it is crucial to butcher at the appropriate time- and appropriate time is measured by when there are zero pin feathers, (2) do a scauld with hot water and dish soap, (3) pluck everything you can, (4) then re-scauld with hot water that contains flexible wax (game wax or something like that), and then (5) do a final pluck of the remaining feathers which in reality should just 'peeled off' of the skin bc the remaining feathers are encased in hardened wax.
Once I get some Muscovies this is the method I will try. Some people only use 1 scauld and the wax is in thatsame scalding pot. I've tried that on wild ducks and for me it just wasted too much wax. The very exterior feathers were the only feathers encased in wax so it took tons of dunking/rewaxing to get to the difficult under feathers. (I was, however using simple paraffin wax and not the newer more flexible wax for defeathering animals).