here is what works for me.
scrape meat off fan, i dont degrease but use borax heavly
spread on board, tack two outmost feathers down with small nails to hold them in the spread position.
use strip of cardboard about 3"x 10" (carding) and lay over plume feathers and tack down.
trim meat off beard but leave white stuff on, coat with borax.
cut legs 1/2" above and below spurs. with wire push out ligament in one bone hole and push out yellow junk in other hole and pack with a little borax. some people remove skin from leg, some leave it on. let dri for a couple weeks. i use a staple gun to mount to plaque, stapledover about5 quils.