Whether you are a beginner fly tier or a seasoned veteran, creating smooth tapering dubbed bodies for flies can be difficult. Some tiers believe that the composition or look of their fly bodies are really not that important but when you start to consider how few chances you get at catching fish every wild card you can control equals better fishing.
The first important point to think about when talking about dubbed bodies is that how your underbody is constructed will determine how the final dubbed body will turn out. Time and time again I have seen people struggle with unevenness in their bodies because they have not done the proper underbody work.
As you are working on attaching materials to the hook shank, work your way from the back of the fly to the front. Wrap down materials with a consistent/even thread pattern and make sure you leave a long end tag end so that as you wrap the material down to the hook shank you have enough to extend to the back of the hook eye. In addition to this as you lay these materials on the hook be mindful of how they sit. If your ribbing spins around the hook shank take the time to set it back to the top of the hook shank or else you will see the twist as you dub over this spot. After you have all you tailing fibers, ribbing, etc., in place make one more pass up the fly body with the thread securing down all fibers so that you have an even body surface to dub over. This last step of creating a thread covered underbody will take you some time if you do it right but will definitely make your life much easier as you dub the fly body.
When you start to dub the fly the best advice I can give you is to use very small amounts of dubbing on the thread at one time. Being conservative in this fashion serves two purposes. The first is that as you spin the bobbin you will be able to get the dubbing tighter on the thread. The second is that with smaller amounts of fur on the thread you are forced to build your body up as you wrap the dubbed thread which makes for a smoother/even body in the long run.
Dubbed bodies add size and realism to your favorite fly patterns. Take the time to build even underbodies and work with small batches of dubbing and I guarantee you will be pleased with the results.