Native American Indians used to soften leather by getting the old women of the tribe to chew it till the hide was soft and plyable, perhaps you could have a word with your granny.
Failing that, you could always try good old fashioned Dubbin as used on real football boots ............ not the pink plastic ones used by today's poncey primadonnas.
Find yourself a local horse riding stable, the people who work in the tack room will be able to advise you and perhaps even supply some Dubbin.