I just finished (mostly) a major application that I've been working on for a little over a year (off and on). It is around 86k lines of code, 50k of those is from Visual Studio's auto-generated dataset. It's largely a GUI to interacting with the database, generating reports, etc. It deals with money and manages contracts so it is important for it to be as bug free as possible.
I've walked through the code, and ran the program myself. I, for the most part, cannot find more bugs. I am however, sure there are, I've just been working on the system so long I can't see them anymore. I know there are some, because of some intermittent issues I run across, but can never pinpoint.
How should I go about software testing in order to discover the remaining bugs?