O.K., here goes.
First, thank you very much for the interest in my flies.
I use nothing but hareline and haretron dubbing. Years ago I decided to use nothing but materials any fly tyer can access. Second, rabbit fur is sufficiently stiff that it retains its integrity but supple enough to be moved by the water to suggest gills on nymphs
The "bugginess" you refer to is how I manipulate the material to suggest gills on various nymphs; however, its application goes beyond this to tying cress bugs and even dragonfly nymphs. Let's just say that the technique is quite versatile.
For most nymphs I apply 2 layers of dubbing. It is critical to apply the dubbing to the thread as tight as possible and wind the dubbing as tightly as possible as the abdomen is formed. Next comes the ribbing which holds the dubbing in place. I only want the "bugginess" on the sides of the nymph. The ribbing must be applied very tightly, as well. With a dubbing needle (I find the best is a T pin used in curtain making) run the point up along the sides of the abdomen. DO NOT pick out the dubbing!! You can control how much material is pulled from the sides by how tightly you press against the sides of the body. Once you have the desired density of pulled material you trim it to length. If, after trimming, you have areas more dense than desired you can VERY CAREFULLY remove a tiny bit of material from either the top or the bottom of that small area. The reason everything is applied and wound tightly is so the needle point doesn't catch either the tying thread or the ribbing thread. This is also why I shun using Velcro for this. Velcro can shred my ribbing and possibly my tying thread on my smaller flies.
I do my own blending and I blend only by hand. I do not use a small blender because, contrary to what some say, they chop the fur. I don't want that.
Hope this helps. And, again, thanks for the interest.
Footnote: The next issue of American Angler magazine should have a photo of my Isonychia nymph which is a good example of this.