I've been working on a '50 Chev that was undercoated when it was new. I've had good luck using carb cleaner spray. I spray the area that I want to work on with the carb spray and let it soak for a few minutes, then take a screwdriver or scrapper and it will come off and expose nice clean metal. I've found that once you get a small spot cleaned off, then spray the edges so the carb cleaner can work its way in it helps. I've had great luck, getting brake lines off, brake hoses, backing plates, splash shields ect. The bottom line is it takes time and patience to do a good job, and its messy no matter what method you use.
Don
