I've always been paranoid about bug problems, so in the past I've went through the trouble to split between each quill and scrape 99% of the meat and fat out - a bird flesher that taxidermists use (really just a glorified wire wheel with a shield for the mess) would probably make quick work of it, but given that I don't have such a setup, it's a pain in the rear and time consuming.
So, I'm now a fan of the pluck and reassemble method. Just pluck each feather and keep track of where it goes, and use the glue/adhesive/filler of your choice to bind them back together - Bondo is convenient and works well. Zero meat, fat, or tissue to worry about and no waiting for Borax to dry everything out.
I also like to wash the feathers in warm water/dish soap and then rinse and blow dry. Plucking each one also makes it easier to "preen" them if you happen to be someone that doesn't like the usual gaps and separation of the barbules that they all have to one degree or another - giving them the ratty look sometimes. In most cases, they will "zip" back together pretty easily by just lightly pinching the separation between your thumb and pointer finger and pulling outward from the base to the tip.