Here's a softening recipe from a 1941 A. H. Harding publication.
'MIX'
Soft soap (not sure what is meant by this)....1 pint
Neatsfoot oil....1 pint
Alcohol....1/2 pint

so.... 1 part oil and soap to 1/2 parts alcohol for whatever amount.

Apply enough to wet the hide well...let stand for 24 hrs... remove any excess by scraping...continue the breaking process