Second vote for eternabond here. Make sure you get a metal or hard plastic roller, though. Rubber won't do the job well enough.
For figuring out where the leak is, I have seen pics of someone who made his own pressure testing setup by using an electric blower, putting it through a piece of plywood and rolling it up in his passenger window. You could even buy a couple of blowers (more power is better in this case) and rig them up for less than the cost of a professional doing it for you once. Then you could reuse that setup each year. Wait ...... now that I think about it, I might make a double blower rig myself.
Jose
