I have tested neatsfoot oil for sealing old pouches, but I firmly
believe that replacement of pouch leather after 80-100 years service is
preferred.  It's a matter of time, not use necessarily, that causes the
deterioration of components.

I feel that if you get into the workings at pouch level, then you may
as well replace them to guarantee an extended period of service.
Unfortunately there are no shortcuts that should be attempted. The old
school methods and techniques were adopted after laborious testing and
should be adhered to today. 

Paul Brennan