Howdy, Pard,
Neatsfoot oil was/is intended to prevent cracking in the hooves of horses and cows. But those are living tissue, which re-grows itself. But neatsfoot oil by itself attacks the fibers of tanned leather, and eventually will destroy it! There are a number of preparations that don't do that. I have been using Lexol(R) Leather Conditioner on holsters and belts for over thirty years. LIGHT applications, either spread on with a soft cloth or sprayed on (from a pump bottle they sell with it) and the excess wiped off will keep the leather moistened, but not damage the leather. BUT YOU CAN OVERDO IT! LESS IS BETTER!
Saddle soap should only be used to clean VERY dirty leather. Fiebing's glycerine saddle soap, applied by rubbing a damp cloth on the soap bar and then applying it to the leather, followed by wiping it off, allowing the leather to dry, and then applying the Lexol Leather Conditoner is the best treatment I know.
Hope this helps, Pard!