Mindset, experience, equipment(money), patience, willingness to "eat" a few hours, and humility to ask for help from those who have done it awhile.
Get an H10 and learn how to use it. KISS. Slow the down. Stop, look, listen, observe and think. Where are the weakest points. High pressure first, then pressurize the low side (more is better). Spend a few hours on HTALK doing searches. Don't run away from an opportunity to put your skills to work. It's a finite, fixed, sealed system that was more than likely installed by a human...it CAN be found, repaired or replaced. No magic, no problem. Good luck!
Also...spend the time to actually KNOW how the leak detector works...read the manual.