If you don't care for the cleanup, good old Cosmoline or RIG grease. However, if you have a good tight box or case to store them in, say made from wood, or a cabinet, you can use several good sized bags of Desiccant, after oiling them well. Once a year, the Desiccant needs to be taken out, and run the a clothes drier, but they will remove the moisture from the atmosphere around the guns, and stop the rust. Last, you could use a combination of both.
I also read about somebody packing them in plain Vaseline, and they didn't rust. Plus, a good paste wax before any of the above will help.