I used to stretch, salt, scrape - repeat, n repeat, n repeat...and got something as hard as a board and smelled like the dog on a bad day... What is the ratio of Ivory soap to water ? That's a new one to me.
I had an old scout master who said just piss on it. Not sure if he was just deep in his cups or was serious. Tanning hides was a specialty trade in the Middle Ages. Even had their own union.