If you look up the worst painter in the world, there is a picture of me.... With that in mind...
In the basement for the winter.... I have part of a gallon of International red, and part of a gallon of JD yellow paint..
When needed, I just cut the skin off the top of the paint, and use as it is.. The prep I use is to go over as much as I can with a wire brush on a 4" side grinder. Then a rag of acetone or alcohol depending on what is available. When dry, I paint and let dry for a week or so before moving.. It actually takes 2-3 weeks to be set the best.. I'm not impatient about letting it cure.
I'm not particular about color, or show room quality of the job.. Protection of the implement is my concern.