Winging and skinning a thornback is easy.
Cut the head and tail off following the wing to leave a butterfly shape, the bit joining the wings should be about 1½ to 2" thick.
Cut the leading edge of the wings , about ½" in (not always needed but makes life easier for amateur Skinner's)
Cut through the skin (only) either side at the root of the wing (4 cuts)
Cut skin (only) from wing root to tip (again, makes life easier)
Now, the important bit. Use a pair of skinning pliers to pull the skin from the flesh. Start from the root of the wing pulling towards the tip.
This should be 8 pulls if you have done your cuts right!
At this point you should have 2 wings attached by a central point.
All that is needed is to portion up as required and vac pack and freeze
Hopefully I've made it sound simple because it is.