Preventing corrosion during a build?

I will be rebuilding a 440 over the coming months. I showed pics of the inside earlier and someone commented that it looked dry inside. My question is what do you put on the iron parts during a rebuild. I have heard that WD-40 is corrosive, so no go there. I will use assembly lube on the cam etc.. But when you remove a part and have cleaned and degreased, the heads, for example , what do you use to coat the head while it sits on the bench awaiting re-assembly? Sometimes just the humidity in the air will cause surface rust. A spray would be great.