If a DC bothers me when I am trying to focus, I will often explain to them that they are not actually a person. I will offer some proof, "like look over there, it is just blank. Does that make sense? Of course not, now stop bothering me." This almost always gets the DC to look upset and get real sulky and queit, but at least they leave me alone. It back fired one time and the DC became really concerned and started asking me all sorts of questions.
Last night I had a sexy female DC and we were ~censored~, she was barely moving and totally passive. I stopped and said "I release all control over your actions, please act and speak naturally and randomly." The DC really came to life at that point. She was very actively engaging me, kissing, making suggestions, and so on.
I like getting a difficult DC to do what I want by randomly making something up. Say a guy wont let me in a building, I may say, "Hey Chuck, I'm so glad your here. They are just down the street and around the corner, if you hurry you can catch them." And more often than not the DC reacts how I want.