There are several methods. First method I usually use is: to spray a hard wood with a 50/50 solution of water and denatured alcohol, and place it in a zip lock type bag for 4-5 hours. Another solution is 50/50 water/ammonia, but I didn't try this. Also, I heard about one tip that sounds crazy, but ppl say it works too. First soak the wood in water for 4-5 hours, then put it in the freezer for another 4-5 hours, then it becomes much softer and easier to work with. In any of these cases, you should dry the wood when finished and apply a sealer to prevent cracks from showing up in the future. I usually choose sealers woodyexpert suggests as good ones for finishing wooden pieces. P.S. If you try freezing, let us know about the result please. I'm really curious.