The best photographs require a digital camera with a manual override, a tripod and a remote switch.
What I do is:
Place my subject and mount the camera.
Use the autofocus of the camera to focus the subject with the lights on.
Switch the camera to manual focus.
Turn of the light and charge the subject.
The next two steps you'll need to play with to get the best photo.
Vary the shutter time to capture more light. The longer the shutter time the brighter the picture will be. If you set it too long then the GITD paint will wash out and appear white.
Vary the F-stop. I typically use an F-stop between 4.5 and 7. If your camera does not allow you to change this then play with the shutter time.
Rinse and repeat until you get the picture you're looking for.
Westend summed it up well. Long exposures are the rule with most of mine around 90 seconds. Play with the ISO speed, f/stop & exposure time until you get the results you like.
FWIW the first image is normally not what you want (the trit is usually underexposed). It takes me two, three or four tries to get it right.
Use a shutter speed of 2 seconds in a dark or dim room. Use another flashlight to illuminate the subject, but not too much that you wash out the GID effect.