Now we need to protect any exposed metal from air and water to prevent any further damage due to rust. I had some epoxy appliance paint from another project. Now this is not the best choice since it cannot tolerate direct contact with water, but I figured that it was protected by the black gasket and the plumber's putty. A better choice would be to use a two-part porcelain chip repair kit. The drying time for this method could over 8 hours.

I added tape around the hole to protect the other parts of the tub. Then I cut a hole in the brown craft paper to avoid any overspray.

Spray the drain hole and waited until it was completely dry. If you spray multiple times, there will not be any drips and the drying time is reduced. After drying we are ready to start to reassemble the drain. I found out later that any paint that ended up exposed to water just flaked off.