JDM777
I am sure there are about as many answers as there are members that have painted their frames. I am a very big fan of POR-15. It is very durable and it encapsulates the rust. Keeps more rust from forming. If you are just a do it yourselfer, you can use a foam brush to paint it on. Leaves a minimal amount of brush stokes, unlike a conventional brush makes. Try to apply it as directions recommend. Keeping in mind the temperature where you are painting it, etc. Just a recommendation. I am sure that there will be others that have had equally a good luck with another product. Good luck with your project. Remember, the prep is the key. Do all the little things right and the end result turns out nice. Hope this helps.
Rugo