Rain and fog drifting through the Pre-Alps made this a distinctly unspectacular venture.
I recommend to take the BOB-train from Munich to Bayrischzell, then to pedal via Ackernalm on the toll road until the marked path departs from the road and reaches the summit in roughly an hour. Descend eastwards via Erzherzog-Johann-Klause to Kreuth (short "non-bikeable" strech) and fetch the BOB back to Munich in Tegernsee.