I would soak the captive nuts in PB Blaster or Kroil penetrant for a day or so beforehand. WD-40 is about useless for this. I would also consider loosening the bolts along the upper edge of each wing where it attaches to the inner fender so you can shift the wings out a bit (you might have to remove the first few). That will make it easier to remove the apron with those beadings flapping around. Of course, if you have the inner fenders dum-dummed to the outer wings, this may not be possible to do easily.
I would also consider pop riveting the beading to the lower part of the wing after you remove the apron if you were able to move the wings out. With the wings pushed out, assembly will be much easier with the beading held in position. I pop riveted the beading in place, and was able to get the apron on without any help and didn't have to worry about getting the fenders all scratched from the sharp tabs of the beading.