I filled the bottom of the trunk with water putty to make a solid base. I wasn't worried about it toppling over, but I didn't want the outer shell to crack if it were bumped or squeezed in the wrong way.
To achieve a good base color for the bark, I mixed Zinc and Bittersweet Chocolate by Americana. I stippled the paint onto the tree to avoid leaving obvious brush marks. After letting the paint dry, it was easier to see which areas were missed in the first go around. I dry brushed some Zinc mixed with Mississippi Mud to highlight. The lighter paint brought out the bark detail. It looks solid and treelike, no?
Now, it's ready to sprout leaves!