Fletching a blowgun dart with cotton is the same basic process as fletching a blowgun dart with thistle, but it is considerably easier. Many people don't realize that cotton was a native crop in the New World. In fact, the earliest know domestic production of cotton occurred in Mexico several thousand years ago. The Cherokee were raising cotton by the mid 1700's, and both they and the Choctaw used raw cotton fibers to fletch blowgun darts.
I like to fletch darts with raw cotton because that is the traditional way. If you have access to a cotton field you can pick the cotton boles and clean them yourself, or you can go to a cotton gin and get some cotton that has already been ginned. If you can't get raw cotton you can always use store bought white cotton balls. They will work fine, but that snowy white fletching just doesn't look right to me. Pictured below: top, Unginned raw cotton; bottom, ginned raw cotton.
Once you have obtained your cotton, you want to pull it apart to kind of stretch out the fibers before you start applying it to a dart. Pictured below: Stretching cotton fibers.
When you have your cotton prepared, take a dart shaft, split the end, and wedge your string in it just like for a thistle dart (see previous post).
Now you are going to hold the long end of the string in your mouth, the dart shaft in your right hand, and the cotton fibers in your left hand.
Slowly roll the shaft away from yourself; and as the string wraps around the shaft, insert cotton fibers, a few at a time, under the string. It takes a little practice to keep it smooth.
Continue spiraling the string down the shaft until you have about two inches of fletching on the dart.
Next wrap the string around the bottom of the fletching several times and tie it off with a couple of half-hitches. Apply a dot of glue to secure the knot.
Twirl the dart to fluff the fletching, and then smooth it down.
You can use a sharp knife or scissors to trim up the fletching, and then you are done.
The only thing remaining is to insert the dart in your blowgun and test it out.