Ray normally CDC (Which means literally ducks arse or ducks *** in your language) are very small sparce feathers. Mark Pettijean (the magic tool man) does sell some larger ones, but I find they have a much thicker stem, and even these you need at least two feathers.

I have got the marryat tool, which does work and its easy to use, however the folding of the feather at the end so you can cut off the stem leaves you with very short fibres in most cases. I also have the magic tool from Marc Pettijean and this works great, but you still need two, three or more feathers to make a decent body or wing.

Oliver Edwards in his videos demonstrates taking out part of the centre stems creating a V shape in the feather and tying them in then pulling the feathers back so the thread comes off the stems, but he uses several feathers stacked.