I second the recommendation for Musher's Secret. I keep some in shallow, wide mason jars so I can dip a little bit out and coat paws. I don't worry too much about her paws in the snow, but some of the plow drivers use WAY too much salt around here and the roads are caked.
I'd recommend purchasing dog booties (I have a RuffWear set that's lasted me 6+ years and looks like they'll last another decade). I don't put them on unless she cuts one of her paws, which has happened a few times over the years, always on sharp ice while hiking. If you acclimate your dog to wearing booties when young, you won't have a battle if/when you need them.
Snowshoeing with dogs is GREAT fun, one of my favorite things to do in the winter. Winter camping is even better.
Bring some good, high calorie treats if you're planning to spend full days outdoors. I usually bring a thermos of soup/broth, and I'll give my dog her snack soaked in warm broth in a collapsible cloth bowl for lunch. Good for hydration. I also bring hardboiled eggs for dog lunches (peel at home, then put them in a ziplock bag in your pocket, they'll stay cool but not frozen, no mess, and contain liquid).
I've spent consecutive days - weeks - winter camping with a GSD, including in the Boundary Waters Wilderness (MN / Canadian border) in subzero temperatures. If you plan ahead, have the correct gear, and make absolutely certain that your dog is getting plenty of good food and liquids, they're wonderful, rugged outdoor companions. The sky's the limit.