The best solution would be to use saw dust and wood glue. You make a paste with it and apply it to the crack. You'll want to use an exacto knife or something to make sure the crack is clean and smooth. Apply the paste and then sand it when its dry. The advantage to using this is that the wood/glue paste will expand and contract naturally with the wood.

With that said I used epoxy to seal one of my didj cracks and its worked fine ever since.