Changes

One possibility is catching a ride towards Salzburg to the next gas station. Plenty of cars stopping there into BOTH directions (north and south).

But the best is to go from the city center almost directly to the east along Faakersee-Bundesstrasse (Ludwig Walter Strasse, then Maria Gailer Strasse) over the river and before the fork to the Sud-Autobahn there is a bus station where you can hitchhike and cars can stop and pick you up.