If your just looking for an easy might work kinda thing you might try soaking/flushing it in kerosene. If the engine is that slugged up it might be too late anyway. It really depends on how much time you want to spend on it and if you want to take it apart and clean it right.
If you do get it running I would run it with diesel oil. Diesel oil has more detergents to clean your engine and keep it clean. You can also run a quart of Marvels Mystery Oil in the engine, I personally only do it for a few hundred miles, MMO is thin and will evaporate more than normal engine oil but it cleans good.