In my experience, Germans are much more direct than American girls. You may want to to tone down the PUA stuff when you're dealing with them. Sometimes game is more about logistics than it is about coming up with the perfect text message. My advice is to make a plan that involves you and her and is either at your place or close to your place. If she gives you excuses just counter with something like, "blah blah blah, I'll be here at 9pm. Meet me." or "no excuses. I'm coming to get you." If that doesn't work, she's just not interested it. Move on to the next faulein.
ps - Where are you meeting all these Germans in DC?
ps - Where are you meeting all these Germans in DC?