There is hardly anything to study for in the Mesaba interview. No 121 regs. No trick questions. Know the electrical systems, gear operation and systems of all aircraft in your logbook. My interviewer chose and aircraft model I had logged 2.1 (a one-shot BFR in a customer's own plane) total in, but since I logged PIC I sure as heck better know the systems. Luckily, I did. If you happened to sit right seat on a King Air and logged it PIC, you'd better be prepared to explain all its systems.

Think about 4 eventful flights in your past, and you can base all the TMAAT questions on that.

Read the gouges on aviationinterviews and you'll be fine. If you fail the interview, I'd say it's more because of your personality. They hire lots of people who go full scale on the sim. The trick to the sim is to always hold some left yoke (it has a right turning tendency), don't touch rudder, and trim it as soon as you hit your altitudes. Once you trim it, it will stay frozen.