So, I made a tree trunk today. I experimented with using plaster for a bark texture, with mixed results. That's why I only got one done. I ended up going with my usual technique, using dowel rods, aluminum foil, white glue/water mixture and tissue paper.
Step 1). Grab a fist full of dowel rods and bind them together using rubber bands.
Step 2). Wrap the bound dowels with aluminum foil, at least a few layers. If you use too many layers, you start to lose the definition of the dowel rods.
Step 3). Mix white glue and water. Then wrap tissue paper over the aluminum foil, and paint on the glue/water mixture using a sponge brush.
Step 4) while the tissue is still wet, I sprinkled some tile grout to give the bark more texture.
I ended up painting the trunk while it was still wet, because I'm impatient. It's not recommend, but my results came out pretty good. Once it's all dry, I'll give it a dry brush, and add some moss. I'm going to keep the dowel rods in, but they can be removed, for a hollow log affect.