I might sound like I am getting senile and repeating myself, but Marc Petitjeans book on tying with CDC is arguably the standard for any book on the subject. Marc has researched, played with and come up with, and popularized the use of these rather unique feathers. If you want to learn literally dozens of ways to tie with CDC, then grab yourself a copy and dive in.
Today I want to highlight the funnel wing technique of tying with CDC. This technique eliminates the often rather bulky stem of the feather from the equation, and affords the tyer the use of only the most important piece of the feather, the barbs. When tying your wings in this manner, you significantly decrease any unnecessary bulk, making an already light pattern even lighter and much more of a finesse imitation.
In order to do this properly you will need a few of things. The first being a pair of closely matched CDC feathers, both in size and good quality. Try and choose a pair that have an abundance of longer fibers, with minimal to none that are broken. If the CDC you have is rather sparse, you can always add a third or fourth feather to the stack as we are going to remove the stem.
The second part is a tool that will allow you to grasp the fibers uniformly so that you can trim away the stem. For this you can spend a significant chunk of your play money on a Swiss CDC Clamp, plastic material clips or whatever other new gadget the industry has in the pipeline. The former will run you anywhere from $45-$55 depending on where you purchase and the latter about half that, but you will get several as opposed to one. Or, if you are a bit thrifty, you can purchase a multipack (https://a.co/d/7OAY87d) of various sizes for under $15. You will not only have more than you will ever need, but you can use them for a variety of other things in the house like chip bags, bagged baking ingredients or paperwork. Just be sure to get the ones that have straight edges without any indentations or other varied surfaces as they will not work as well. A selection of sizes will come in handy for a variety of other materials as well, and if the spring wears out, simply toss it in the trash.
The last tool which I say is optional, and others would say clearly is a necessity is a folding block or material table. Same situation here, you can purchase one or many of these for as little as $10 all the way north of a $100 as some are discontinued and hard to find. Or, get yourself a sheet of block foam, cut it into a triangle and run a slit through it at 1/2 inch or 1 inch intervals. There are a litany of foams to choose from, in a pinch you could adhere a couple sheets of 6mm foam together and cut it to size after for under $10. Feel free to get creative but don’t think for a second you need to spend a ton of money on some crazy tool to accomplish the task, it simply isn’t necessary. What this tool brings in is the ability to fold your fibers over onto themselves, and remove the stem with double the amount of fibers going into the winging process. I say optional, because you can accomplish the same task without it merely add double the amount of feathers for more fibers, and perform the task twice, or in this case use a block and grab them all in one shot. You pick what you like.