I managed to get a Suzuki Bandit (Suzuki not known for their durability of finish) through two Welsh winters with almost no deterioration, even though the bike lived outside and was ridden daily on muddy and salty lanes. The method took half a day in the autumn and another half day in the spring, but with a bicycle it would be a lot quicker. Basically, I gave it a very thorough clean and then treated every surface (with the exception of seat, braking surfaces, controls and visible paintwork like the tank, which are easy to wash down anyway) with ACF50. This is a spray preservative developed for rustproofing airframes, and it's quite expensive, but a can would last several years for a cyclist. Think of WD-40 but much heavier and stickier. It's nasty stuff to apply, being a kind of sticky pink foam, but one application will last the winter. Once it's on, don't touch it. Hose down if needed, but no detergents. In the spring, use white spirit to clean the whole bike down, dismantling as necessary to reach the hidden bits. The bike emerges like a butterfly from a chrysalis and you are good to go for the summer.
Having said that, I will be riding through the winter and just cleaning and re-lubing as often as I can.
