The only problem that I forsee with the bubble soap approach is that your leak is going to have to be fairly signifigant, sounds like your's is, and getting the bubble soap everywhere it needs to be. I guess you would start with the obvious places like fittings and know places where the hoses rub through like on the passenger frame rail and right around the compressor. If you have a condenser or evaporator leak it might not work as well. The last time I used the bubble soap method I was about 10 years old crawling under one of grampa's rentals with the bubble soap and a flashlight looking for the leak in the gas line, I have to admit it did work.

Mark