My cockpit time in airliners and business jets is rather limited, but I really liked the free service of SimBrief for flight planning. Just toss in origin and destination as well as your aircraft type, and you get beautiful routing as well as proper documents to guide you along.
But even better is the free API. Almost everything you can see on the SimBrief site can be accessed from a remote program - like the Missionsgerät.
After some minor modifications the Missionsgerät is now able to access this interface. After finishing your flight planning in SimBrief, you hit a single button in the Missionsgerät and - voilà - not only your flight plan has been transferred, but also aircraft and weather data, navaid frequencies, callsigns and lots of more details.
I built a small manual on how to download SimBrief flight plans to the Missionsgerät if you are interested. And I would love to hear your feedback.
(Please note that the Missionsgerät as of now does not import SIDs and STARs as the custom missions cannot handle them yet.)