I couldn't figure out how to run findbugs against Oozie. And even if it does work, it looks like it's just going to create an XML file.
Based on some minor refactoring to this tutorial and this stack overflow message, I was able to improve our findbugs reporting. Now, when you run mvn verify (which we use to generate a checkstyle report), it will also run findbugs and transform the resulting XML files into html files that are human readable.
The hard part here will be actually going through the reports and fixing these bugs; but that's for other JIRAs