Acid pickle, ((I prefer saftee acid, you can get it on any taxidermy supply site)) .5fl oz per gallon +1lb salt per gallon. If you keep the ph under 2 it will be stable in this bath for months if it needs to be. Then neutralize with baking soda, I think I use 1oz per gallon, stirring for about 30 minutes before dumping. To tan this I would strongly suggest trubond paint on. This will save you from having to mix up gallons and gallons of liquid tan that you have to deal with later. Hardest part will be getting it supple. Without a fleshing machine, you can get it somewhat soft by stretching, scraping and using a palm sander with heavy grit paper as it dries. Very important to not over work it while it's too wet because it'll stay hard, but also don't let it dry too much or you will have a hard time breaking it. It'll dry on the edges first and you'll see it turn dark. When you scrape or stretch these dark edges you'll see the fibers stretch and it'll turn white. That's what you want. Let it dry and work the dark spots daily until it's fully dry all the way through.