First of all, that is a good friend to give you that prop! I found a tutorial that might get you started. It is for a tree stump, but the technique could be applied to a whole tree. http://www.halloweenforum.com/tutorials-and-step-by-step/103804-tree-stump-3.html, here is another one that might be helpful. http://www.halloweenforum.com/tutorials-and-step-by-step/109371-my-haunted-tree-8.html