The best finishing product I have ever seen is japanese lacquer, those traditional craftsman always apply on horn bows or Yumi.
Tung oil is secondary choice, as lacquer is much more expensive and sometimes causes deadly allergy.
I have tried wax oil once and I found it looks great and well waterproof, but I'm not sure about its duration.
In addition, I saw someone apply heated bee wax on the wood self bow and it looks nice, too.