Mummifying is a good option – either whole or in parts (wings/feet/etc)
You could clean up the bones, I accidentally cleaned some g.oldcrest bones once (including skull) by just putting the carcass under a tub. The danger with that is, because it is so tiny, you run the risk of the maggots breaking the skull.
You could find an ants nest, skin it and put it inside something with small holes to let them clean the flesh without running off with smaller bones.
You could macerate, either just loose in a tub and make sure you strain the bones well when emptying the water, or inside some tights or other mesh like material.
You could, even, skin and deflesh as much as you can, and use the oxidation method:
http://www.theboneman.com/Oxidization.html
I’ve not tried this myself but I want to. I’ve cleaned some mummified bones (including a blue t.it skeleton) by just soaking them in peroxide and picking off what I could.
Good luck anon! I hope it goes well. I have a w.ren in my freezer I’m going to attempt to clean soon, fingers crossed for our tiny birds