An angle grinder with a cupped [knotted] wire brush. It would get about 1/4" of paint at a time, so I had to do it in strips- picture eating corn off the cob (typewriter method). Took the fittings off with an O/A torch and some pliers. The pliers were too short and I'm now missing knuckle hair, but that's a different conversation for a different day.

I touched it up the areas that saw actual heat with some waterproof 160 grit sandpaper (the stuff that comes in a rolled strip about 1.5" wide- the stuff plumbers use to prep pipes before they sweat them). Worked well- no paint fumes to speak of.