Fletch said:*The Army issued a compound called dubbing for waterproofing. Shoe repairs don't sell anything called dubbing today. An 1881 article on leather tanning says that "The grease called dubbing is composed of equal parts of cod-liver oil and melted tallow." Tallow is the highly rendered animal fat in soap. I don't see why mink oil wouldn't work as well, or maybe better.
You can find dubbin (no 'g') in camping shops all over the UK, and I've just found a US company that still makes it - Pappy's Dubbin