There is certainly no substitute for pounding the pavement and hustling. Obviously, getting the word out on social media is critical. Mobilize your fans in each area that you are visiting (reach out to them one-by-one if you have to) to help you publicize the event. Turn your fans in each area into your virtual street team.
But, aside from those basic ideas, there’s another tactic that might work for your situation: promoting your tour by shining the light on other artists.
For each stop on your tour, share the bill with a local musician from that area—preferably a musician that has a complementary music sound to yours and has a decent following. Publicize the show on social media by emphasizing this other artist as much as you emphasize yourself. You can have this artist open for you during the show, or you could even open for them.
By involving a local musician in each performance, you are opening yourself up to a new crop of fans, boosting your show’s attendance, and engaging in some great inter-city musician networking in the process. It is a win for both musicians involved.
Best of luck with your tour!