yeah, petroleum jelly or Vaseline is probably the best thing for it, although I would recommend putting it on them before they get frostbite (it helps both ways). I have several chickens for show that I keep separated from the others in cages, and I have the similar watering system you do,only i've never had problems with that specifically. However, when we had a cold front come through here in Ohio a few weeks back, almost all of my roosters have a tint of purple on their combs and wattles. The purple parts will eventually dry and fall off, and the rooster will likely never regrow it. The thing is, after their comb becomes completely frostbitten, that rooster loses its ability to fertilize eggs. You will still get eggs, if you feed them layer grain, but their might not be as many due to the rooster losing a prime factor needed to reproduce. Argo, the rooster is more or less useless now and is nothing more than a waste of time and energy. BUT, that is only if he is COMPLETELY covered. halfway frostbite on their comb or wattle is far less severe and they have a large chance of overcoming the frostbite and continuing on with their daily lives. Make sure you know the difference, because it can be a hard hit if one of your only roosters loses the only thing that's been keeping him around. I have been careless and I let one of my prize show roosters get it and I used to have the intention of breeding him, but I am forced into other options now. Hope my advice helped!