Changes

Take a regional train (e.g. RE7 direction Dessau, check fahrinfo-berlin.de for route information) from the centre and get off at Michendorf (requires BC/ABC ticket). Leave the station at the left side (in direction of the train). Turn right into the Potsdamer Straße and walk south ≈1.7 km on Potsdamer Straße until it ends (it bends right and is called An der Autobahn then). Keep walking straight ahead on a footpath and cross the tunnel under the Autobahn A10. After the tunnel, turn right on a sandy path through the forest. Follow the track until you are at the Mcdonalds at the [rest area. The petrol station is after the restaurant and seems to be better for getting rides. Your best bet is to either ask truckers (although they might not know English) or stand by the exit with a sign that says "Polska".