Our school is doing exactly the same thing. We are located way in the end of a dead end, in a not very populated neighborhood. Sensei tried to organize a seminar two months ago, and he hanged a sign at the entrance of the street. Not a lot of people attended the seminar, but the sign is definitely working. People come to ask informations and watch classes and enroll much more often.
Now, do you have kids training with you? If not, I am sure that some of you training have children. Give them flyers to give at school. People often enroll in a martial arts school after enrolling their kid, and after watching them train.
Thank you for opening this thread, because I too would like to have some ideas.