Solo,
If you do use the Rustoleum, avoid the Rusty Metal Primer. It apparently has a fish oil base in it to prevent rust from spreading. Other brands of top coats may not stick to it well. I don't think the other primers they produce have the fish oil. Also avoid the alkaloid based primers and paints they offer. Rustoleum has an informative website which describes all of their consumer and industrial coatings and usage recommendations. For what it is worth, I coated some spare parts which are stored outside with the brush-on Rusty Metal Primer. By golly, they haven't rusted yet!
