"Secret concoction"
I learned this from a New England furniture maker and it works well for wooden handled tool as well as fine furniture.
I mix 2 parts turpentine with 1 part linseed oil and 1 part spar varnish (or any oil-based urethane varnish). This makes a thin solution that spreads easily and can penetrate fairly well. As it was explained to me, the turpentine (or mineral spirits) helps the linseed oil dry more easily. The linseed oil makes the urethane more flexible and resilient. This combination is very protective, especially from water, and can be restored easily. Apply and let dry. Brush with 0000 steel wool between coats.
In a similar vein, the historic Plymouth Plantation in New England makes a finish called "Miracle Finish" from melted beeswax, turpentine, and linseed oil. I haven't tried this yet but I've heard its quite good. I think the ratios are about the same. Might have to mess around a bit to get it right--I like the more natural approach this provides.