Brush painting and wet sanding with steel wool was the standard repair procedure for repainting cars before WWII.
This is a page from the 1926 Sears and Roebuck Catalogue
Other than whale oil being the base of the enamel from that era, the Rust-Oleum paint would be basicly the same thing as what would have been sold back then.
I had a friend in high school that took 1/2 gallon of Rust-Oleum and spray painted his Bug-eye Sprite with it using Coleman lantern fuel for thinner. It was a good thing the color he chose was orange because the resulting finish had a matching orange peel texture.
Al Lieffring
66 230Sl
Jones'n for a new gas tank