I would drain the tank, put in some very pure isopropyl alcohol, swish it around, drain it as dry as possible, bag the tank, and use some dessicant. That should put it in good shape for the winter. The idea is to keep as few water molecules in the environment as possible.
Another option if it's available is to replace the oxygen and/or water with nitrogen. Being an inert gas, rust won't form in that environment. Some tire shops will fill your tires with nitrogen, which makes tire pressures more stable over a longer period of time. Some say it's because Nitrogen molecules are larger than Oxygen and won't pass through the rubber molecules of the tire. I don't know about that: I'm just passing along the info.
Of course, the bag needs to be airtight. I'm sure there's other caveats as well.
I hope this helps. Updating forums while being lectured to is a bonus, sometimes.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.