How about an airplane overhead, with a banner reading, "www.JWFacts.com". That would be impossible to forget. The zombies wouldn't look it up, but the 14-year-olds would, on their mobile devices, almost immediately.
Often, I think holding a sign is like writing a DA letter. It's not really for the benefit of anyone other than the person holding the sign or writing the letter. It's cheap therapy, a way of experiencing a bit of Liberty, even if it's misguided or counter-productive to others.