One trick I picked up on from Chemistry class and the Rough Science series is 'sacrificial protection', where a piece of more reactive metal is connected electrically (sit it on the iron, piece of copper wire, alligator clips etc) to the item to be protected, and it stops it rusting as long as there is more reactive metal available to react. Ideal sacrificial metals are zinc (which is why it's used for galv iron), aluminium if it's kept absolutely clean, and alloy pencil sharpeners which contain magnesium, or even straight magnesium if you know where to get it. Great advantages in that one wee pencil sharpener can protect an entire engine if it's kept clean, rather than trying to coat the entire thing in oil etc.
If Im not mistaken, the sacrificial anode can only work when the entire part is surround by an electrolyte (water, sea, damp earth etc). It cant help in open air, nothing to complete the circuit
IMHO, Vaseline (dilute with white spirit for easy application of thin film, or good old waxoyl from Halford. When I was a poor apprentice I used waste engine oil on my rusty old cars, filled the sills, inside doors, wheel arches etc made the car stink and upset my gfs but what do they expect in a 5 quid prewar shed