I use a light oil and I do it a couple of times a year. You can also get a sheet of VCI paper and cover the top with it. I also am very careful about setting things on the iron surface. You never know when your drill or hammer will have a small amount of moisture on it that will create spots of rust.
I am tempted however to suggest that since the old gentleman was successful using fogging oil that it would be good to take a tip and continue that approach. Hard to argue with wisdom and success.