I initially set Auto ISO but found that the camera just couldn't meter the explosions accurately, so I went with all Manual: Aperture f8, Shutter 4 seconds, ISO 100. Lens: 17mm (Which still wasn't wide enough for how close I was), manual focus set to infinity. Next time I might try f11 and 8 seconds. A tripod AND steady hands are a must.
There were many occasions when the sheer amount of explosive light necessitated that I drop the exposure, but they were impossible for me to anticipate. Maybe I can do it when there's musical accompaniment.