I have found a way to prevent cotton fever that is 100% effective. For the last year I've been adding 1/2 to 1 unit of rubbing alcohol to my shots. I haven't gotten CF once. I realize that it's possible that I've just been lucky, but I believe that the alcohol is neutralizing the bacteria that causes the fever. I shoot H, Fen, Ds and Subs and it works w/ all of them.
Some may think it's crazy, but you're already banging a bag of stuff that you have no idea what's all in it, what's a drop of rubbing alcohol in the grand scheme of things?
Try it, don't try it; its up to you. I just thought I'd share my findings, as CF is a miserable ordeal and I'll do whatever it takes to mitigate its existence in me. Just don't reply to me telling me how bad it may be to shoot rubbing alcohol. I'm sure it's not recommended to do, but I don't think it's any worse than what I'm already shooting, and it prevents the misery that is CF. Cheers.