First the inside. I used a wire brush attachment on the grinder to knock all of the surface rust of the roof frame and floor. I then used Rustoleum Rust Reformer and sprayed all the effected areas with it. I had a friend with a welder put a plate over the rusted hole by the brake pedal. Next the wife and I patched every single rust hole, bolt hole, etc in the floor with a fiberglass/resin kit. Once it set I used a liquid rubber spray also from Rustoleum to coat and leak proof all the fiberglass patches.