Finally I'm getting ready to tackle the last of all the rust in my 70 GS before paint. I will be replacing rear outer wheel wells, trunk floorpan drop panels, quarter panel skin, trunk filler panel under the rear windshield, drip rails ect. Also i will be deleting the vinyl top because of all the rust and moisture damage underneath. One question came to mind! What are a good way to tackle surface rust inside crevices and cavities. I was thinking about making a 20-30% phosphoric acid solution and spray it with a weed sprayer and then let it dry, epoxy over where i can get to and 3m cavity wax where I can't get epoxy over. Thank you.