Forums on Creative Cow can be helpful for technical advice. I would also check out No Film School and stay on top of articles from Indiewire and Filmmaker Magazine. It might be worth it to join the IDA to get access to their Doc U online and magazine articles in print and online. In Milwaukee, while I am not aware of a regular documentary filmmaker meetup, I know Milwaukee Film was, at one time, trying to do more year-round programming than just the film festival. I'd also recommend you try to connect with Brad Lichtenstein at 371 Productions since he seems to have a very good handle on everything happening doc-wise in your town.
In any case, if you have some specific questions, I'd recommend posting them in the Mentoring Room. D-Worders can be very generous with suggestions.