Have you ever watched an episode of Fitzee's Fabrication on YouTube. He focuses on rust repair. He REALLY explains and shows it at a level we can understand. And he is NOT a hack. I have learned a LOT from him. I HIGHLY recommend watching at least one episode. Try watching this one. It shows how to do his amazing Cut and Butt rust patch welding method. It's the only way I weld in repair panels now. I wish I had had access to a show like his 25 years ago. Please try one episode. This one best explains his genius cut and butt method
Off topic, but I'm thinking I'd like to "up my game" on bodywork this spring sometime, and this looks like it may be just the thing for me, as what he's doing (adding a gas fill door) is exactly what I'll be doing to my '68 F250.