I'm just learning this technique but getting better at it with each ornament I make. I thought I'd document the process so you can see how it's done. This is one of several ways of making the inside-out ornaments.
Here are 3 more inside-out Christmas tree ornaments. I turned one yesterday and the other two today. On these, I painted the insides gold. I left the outside plain, unstained wood. The wood will darken some with age, more of a golden brown color. Each of these is about 5 inches long and 1.5 inches in diameter. I made a video of make one of these. I'll post it when I'm done editing it.