I always use a meter, never a test light. The Jeep has air bags but the ignition system is "old school" and actually could be jumped out from under the hood if you know the wiring really well. I had a "crib sheet" that came with the system that gave good descriptions of what harnesses to look at and the right wire colors to use. Even then, I double checked everything with the meter before attaching anything.
I only trust solder for long term automotive use like this. Yeah, it's a PITA getting into a lot of places with an iron and solder, but given the environment, vibration mainly, I never worry about things coming loose and causing problems. I taped everything, double layered Scotch 88, re-wrapped the harnesses and added wire ties to make sure nothing comes unraveled.
I gotta ask how small was the guy with his legs braced through the steering wheel? If I tried to get in that position I'd need EMT's, the jaws of life and a backboard to get me to the hospital, even without the air bag going off! Although a mechanic friend of mine was short, thin and wiry so maybe he could have done that if the wheel was telescoped out all the way.