In the past I've used Tung oil, or linseed oil (get the kind with no lead in it!).
I recently received a beautiful jo for my birthday (Yeah, my wife gave me a stick!
for my birthday, though it is a very nice stick.
It's a very hard wood, and our head instructor, who does fine woodwork suggested a coat of lemon oil on it.
Si Wilson wrote:
Those blood stains just get so ugly, though!