Try using a few ounces of automatic transmission fluid in the cylinder. It worked quite well on old motorcycle engines, way back when.....
Just a quick comment, though. If you have rust already formed on the cylinder walls, you may well do further damage by trying to turn the engine over. If it seized up while running, no problem. But if there's heavy rust present, you could score the piston badly, were you to insist. If you have only limited movement once you get it freed up, pull the head. That way, it's just a matter of a fine hone and a new set of rings.
To avoid this problem in future extended lay-ups, turn the engine by hand in its normal direction of rotation until it hits the compression stroke. You'll know right away; it won't turn anymore. This way, the valves are closed, sealing the cylinder of from the outside atmosphere, preventing moist air (or condensation/water from the exhaust system) from entering and causing rust.
Murphy was an optimist........