Your goal is to stop the metal contact with oxygen and moisture. So many products can do that. Paint is obviously the worlds most favored product for the job.
You can use oils or grease. The lighter the product, the easier it washes off and will need to be reapplied more often. I use LPS3 or similar products on float and ski hardware and rigging. Its a solvent based spray that turns waxy as the solvents evaporate. Makes a mess, but doesn't wash off easily. If you want something lighter, I'd try CorrosionX or ACF50. I'm sure Boeing makes something super skookum.
I remember a product commercial. Flitz or Fritz or something? I remember it toted that is could keep your guns rust free for months in salt water or something? I wonder if they still make that stuff?