I like the T-shirt idea and really just the attitude of spur of the moment making it happen kind of marketing. Step 3 seems a bit much.

We just started marketing a start-up for the first time and this article led me to question an upcoming situation: If I was unable to secure vendor space at a conference/expo, would it be ethical for me to wear my company t-shirt and have cards/fliers available for people who ask me about it? Would it be appropriate for me to talk to vendors about my company?