Hey so I've been working on my rear window channel on a 66 tempest 4 door. when I cut out the bottom, I looked inside and the top of the trunk area/bottom of the catwalk cavity is pretty heavy with surface rust from water intrusion from the window channel Over the years. I'd rather not cut up the car more so I'm wondering what people have done because this is a common problem. I've tried looking into cavity wax or oil/ATF/kerosene home mixtures but I don't know if they will prevent the rust from growing (the rust isn't structurally bad), POR-15 but no way to really prep the area or apply it properly, rust mort (phosphoric acid) could work but I haven't had much luck applying it properly. Just looking for some ideas, or if not how to remove the catwalk area in a way to be able to weld it back together easily. I'm not really a great body man and the welder I have isn't the best for sheetmetal (lowes blue hawk brand) thanks!