Most people use carb cleaner or starting fluid to find a vacuum leak. What they do is with the engne running, they spray the vacuum hoses. If there is a leak, the engine will draw the product through the leaking area and the RPM's will increase.
One concern is how highly flamible the product is. If it hits the exhause manifold or an area on the engine that is at or above the product's flash point, it will catch fire. Just be careful and have a fire extinguisher made for such fires near by.
As far as placing you hand over the throttle body and the car still runs and doesn't choke out, there must be a rather leak that is providing enough air to the intake to keep it running.