I usually use aircraft stripper to strip a car to bare metal. You have to use a thick coat. Don't spread it around with the brush. Rubber gloves are needed as the stripper will eat your skin. Eye protection is a good idea too. If you don't wear goggles at least keep a water hose handy to flush your eyes if it splatters. It's hard to keep your eyes open when you're spraying a hose in them. If it happens once you'll be convinced to wear goggles.
I scrape the paint off with a scraper that uses single edge razor blades. Some cars can be stripped with just the razor if the paint is old and brittle but even these cars have some areas that won't let go without stripper. I never tried Formby's but I think it's the same as aircraft stripper.
I use a spot sandblaster on rust spots. It has a rubber tip that you press against the panel to keep the sand contained and keeps warping to a minimum. It's slower than a regular blaster but you don't have abrasive sand getting into all the cracks and crevises That doesn't come out till you're spraying paint. It's even worse if it gets into your engine or bearings.