I image it can be a lot like shooting lightning. I havent done that since I shot with film SLRs so I am not sure how to explain it in digital terms. What you wrote sounds right. You will probably have to experiment with the exact shot timing.
I took a couple of firework shots a year or so ago with a point and shoot set on a fireworks setting. Here are those shots with their EXIF.
Camera: Panasonic DMC-LZ7
Exposure: 0.25 sec (1/4)
Aperture: f/3.1
Focal Length: 9.9 mm
ISO Speed: 100
Exposure Bias: 0/100 EV
Flash: Flash did not fire
Camera: Panasonic DMC-LZ7
Exposure: 0.25 sec (1/4)
Aperture: f/3.4
Focal Length: 14.5 mm
ISO Speed: 100
Exposure Bias: 0/100 EV
Flash: Flash did not fire
Hopefully this gives you something to work with.
Melissa