I don't really see, why it hitchhiking out of Frankfurt/Slubice is supposed to be difficult. I hitchhiked a number of times to towards Warsaw, Berlin and further west than Berlin. The gas station towards Berlin is great for asking, you can just stand there by the road as well. From Slubice there is a road with few good spots to stop, before the train station (which is 2-3km out of town), but there are a couple of gas stations as well. Anybody got a different opinion/experiences?