Danish or linseed oil.
Fairly cheap and reliable, danish oil being more expensive but better at water repellence. My trusty hazel stick, (currently by my side as I'm just about to go on a mushroom foray
), is 3 years old and has been finished in linseed oil. The saying goes !treat it once a day for a week, once a week for a month, once a month for a year and once a year for life!!"