I had a similar problem with the back end of a Timberwolf I was building. I never finished it as the need disappeared. It can happen if you go slow enough. Using an electric sander may be a bit rugged due to the small contact area. I used a strip of emery cloth pulled backwards and forwards around the rod - the same way railway signalmen used to polish signal lever handles. It didn't really take long either. With that method, you can at least cover 50% of the rod's circumference and come out with a much smoother finish.

Kevin - VK3CKC