Learning to paint....

You might also go to site of Southern Polyurethanes. Many people on FABO use their products, they have a very good tech guy and lots of info on their site.
Every body guy hs his own ways, and you have to take all info and find what will work for YOU and then get experience. You will make mistakes, BUT they can all be corrected. It is just metal and paint!
Just like building a house, the foundation is key. You topcoat will appear no better than what you did prior!!
Use quality products,they do not have to be the highest pried either. NO... Rusteolum will not withstand UV rays for long as a topcoat.