Hi kerzo , yeah once you actually see the rust , its very difficult to get rid of as it starts inside and works its way out until its visible , as you said it was your light guards , would recommend power coating with the full 11 processes, as for a step and they will always chip with the rubbish on the roads , just wire bush and a good sand with a 60 grit sandpaper or so your making it a really fine key and spray them a lot better finish rather than brush , would apply a rust prevention paint just to help then yeah hammerite but give it two coats on the same day you can't let it dry ,its a pacific spec of application ,
Hope this helps and you understand , not very good at explaining lol
Jamie