Until a few months ago I would have whole heartedly recommended Sno-Seal which I have used on most of my leather items since 2008 & found it great stuff but !!!!.....bought a new tin recently & what a deception !..........completely different formula (colour, texture; smell) & it's more like vasseline than a bee's wax compound . I may just use melted bee's wax from now on or try the Granger's G-wax & hope that hasn't changed.
I would definately go with wax rather than animal fats (neetsfoot, mink-oil etc.) Some of the Aussie leather hat manufacturers make their own leather cream, never used it but I think it's similar to the wax/oil dressing used on oilskin coats.
I don't know what kind of hat you have but not all leather can be made water repellent.