I believe it's called liqua tan.
either way get a bird mounting video from vandykes, I have a couple different pheasant videos. I'd have to go back and rewatch them.
The other idea is to go to taxidermy.net
Problem with borax is it'll still allow bugs in if you miss even the smallest spot!
This was a liquid tan..he washed, then fleshed on a softer plastic wheel turning slower then a grinder so you dont tear, then took it to the tan soloution after cleaning, then tumbled in corn cob dust (you can do this in a 5 gallon pail easy enough). Shake it of dust, get the air dried with a blow dryer, get the foam with the neck built up and in, and putter on. Seems there is a few ways to skin this cat, some better some worse but they all work for awhile.
The videos are worth there weight in gold.
But just curious, how you plan on using the soft skinless skin?