ORIGINAL: blw
From what I've read here, Corrosion X is the best for that. A lot of people use ATF and Marvel Mystery Oil for air tools mixed half and half. If I had access to a can of Corrosion X, I would use that as my first choice.
But, you are right that the castor will coat and protect to some degree. And, it does flush out.
From personal experience, ATF is by far the best as it will not evaporate - it will give years of protection & will not dry out or gum up bearings. Literally FILL the crankcase with ATF, carb & down the glow plug hole. Sit engine upright in plastic bag (yes, the ATF may slowly leak out the front bearing but that is why you fill 'er right up [8D])
Castor will certainly protect the bearings BUT it will also gum & seize the bearings, piston in the sleeve, wrist pin in the conrod, etc. Then you will need to soak the engine is fresh fuel, apply the heat gun, maybe even strip down the engine when you pull it back out of the box.
Why temp fate ? The ATF is the better choice over FAI fuel.
NB: edit for spelling mistakes