Just stay on the rudders, brakes will be useless since your tires will just slide but the plane won't want to pull like it does on asphault since the tires don't have much traction so ground looping isn't much of a risk in really slippery conditions. It's fairily easy, just feel it out once with a touch and go and expect to slide around a little which is a little discomforting at first. Lots of fun once you are used to it. Beware of heavy snow, even a couple inches of heavy soft snow can pull heavily on your tire, but on hardpacked snow/ice you should not have that problem.