I use a local brand from my favorite fly shop. It's touted as a dry fly floatant, but it is so fine in texture(?), that I've found it works great for CDC. They key to using floatant on CDC is too little is usually too much.
Here is the process I use when fishing CDC flies:
After I catch a fish or numerous casts that result in the CDC becoming either slimed or waterlogged, I usually rinse the fly well in the water, dry with my chamois patch, place in my desiccant bottle which is a mixture of the fine powder along with desiccant beads, and shake vigorously (the beads serve to absorb water and keep things from matting together, the powder coats everything with floatant powder (which alone doesn't last very long - only a few casts), I then put a miniscule amount of the floatant on my fingers and rub thumb and forefinger together until only a very slight film remains, then I rub this into the CDC.
Long process, I know, but it revives the CDC every time to its original fluff and I'm good for another dozen casts or so, or fish, whichever comes first.
Fishing with CDC requires extra effort to keep it viable in its ability to float your fly. Some folks prefer other methods and/or give up fishing CDC-winged flies due to the efforts required to resuscitate it, especially after catching a fish. Some just change flies, but in the time it takes to change flies I'm able to get the fly into shape to fish with again.
I have a favorite stillwater that has some massive mayfly emergences each evening and my go-to fly is a CDC-winged emerger I call a parasol jumper. If I want to catch fish on the surface, this is the fly I use, given its success, the extra efforts at rejuvenation are well worth the effort.
Here is the fly:
Trailed behind one of these:
And, here are the results:
Good luck, but just remember - less is more when it comes to treating CDC, no matter what brand you use.