My hubby just finished building a dulcimer for me. After some experimentation with different finishes on scrap wood, we settled on tru oil.
You have to apply many thin coats, so it takes quite a while and we let it sit for a month or so before stringing it up.
Here are the advantages that we found:
You can control the finish, either matte or glossy depending upon how many coats you apply and how much you rub the finish.
You can apply it at your kitchen table, no nasty odours.
You can mix up a slurry with sanding dust and tru oil to fill any small imperfections in the wood.
If you get a scratch on your finish you can apply another quick coat of tru oil.
It has a lovely look and the feel under your hands is excellent. It’s great if you’re after a more natural look. It really brings out the colour of the wood.
Just an additional note, we applied it to the body of the dulcimer only. We applied Dunlop 65 lemon oil to the fingerboard.
We used the same fire precautions as you would with linseed oil...let the rags dry out and store in a metal trash can.