Unsticking an unused engine........

i agree with filling the motor with diesel. if the cylinders drain whatever you put in them after a few days the diesel should go the other way past the rings, from the crankcase up into the cylinders.
the only other suggestion i have is (again) fill to the oil filler cap but with white vinegar. it dissolves rust very nicely over a few days leaving clean metal. also remove the carb and fill the intake to the top too so it can get 'in' every way possible.
neil.