I was saying that you were worried about all the technical aspects of resizing and how to set up your dies, and not to worry about this too much. If you did no sizing to your once fired brass and dented the neck so that it would hold your pill, you could shoot some impressive groups.
If you are looking for a COAL to start out with, I would use one that fits into your magizene. If you want to work out what is jam for your rifle, then back it off at least 20 thou.
I have never loaded for a Creedmoor but if I were to have a go I would use 2209 or 2208. The speed looks to be faster using 2209 but you may be able to cram a bit more 2208 in the case to make up the speed. For primers I would get some CCI BR4 if you are using small primer brass.