Here's one I cribbed from Al Beatty. Let's see if I can explain this.

1. You have reached where you want the dubbing to stop, but still have some noodle left.
2. Loop the thread around the index finger of your non tying hand, then back over the shank of the hook.
3. Trap the loop you have just created by taking one wrap around it where the two ends of the loop meet at the hook shank.
4. take a couple wraps around the hook shank as you normally would.
5. Cut off the loop you have created taking the leftover noodle with it.
6. You are left with a nice clean transition from dubbed thread to bare thread.
7. Finish the fly as normal.

Clear as mud?