The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
Well, I use a dubbing brush fabricated as Leisenring did. These are very effective for strong, well-tied bodies. Occasionally, I dub to the tying thread, but for wet flies & flymphs, the Leisenring method works best for me. While many feel a dubbing loop technique is the same, it's not, really. I believe the result of the Leisenring dubbing brush is rough, buggy, and more effective. I also find it easier to control the distribution of the dubbing along the tying thread better using this method.
The dubbing "brush" is the result of the Leisenring method of dubbing. The brush is made off the fly and tied two the fly. Leisenring did the process of creating the "brush" on his pant-leg. Here is a link to the process:
Later, a dubbing block was created by one of Leisenring's students, Dick Clark. I'll see if I can locate a photo. There is a photo and explanation for use in Dave Hughes' book WET FLIES.
Again, I find the results are very good with this method and there is more control over the process. Another advantage is you can make the dubbing brushes up ahead of time, to be used, later.
I'm so glad I've been able to help you. It's truly my pleasure to help others enjoy these flies.
I was upset to see that his website troutnut.com/libstudio is no longer running (and gone with it are all the good pictures he posted in this forum).
I hope it can be accessed by non users too so others can still get to it too.