Have had some experience with Cosmoline. This was 1979. I drove my Healey 3000 from the Left Coast to the other Coast, and shipped it to the UK for Austin Healey Weekend. Took substantially longer than a weekend, I might add.
After exhausting pretty much every opportunity for Austin Healey revelry, I proceeded to contract shipment of my BJ8 to Los Angeles.
I collected my car and noted an especially thick application of noted Cosmolene to pretty much everywhere on any exterior surface my Healey. Took 3 days to remove, but left , ahem, stains upon my gracious host's driveway. Have apologized regularly. Christmas cards and such. Southern California sunlight eventually dealt with that. But the Cosmolene was effective in protecting my car from the effects of the sea salt. In reality it doesn't matter at all, as I eventually embarked upon a full scale restoration, so we attacked any corrosion, and I still own and drive this car. Probably newer products. But Cosmolene does work!