It sounds as if you are doing everything right! If you are allowed to sell gift certificates at the health fair, I would. You could offer $10 off any 1-hour massage IF they book with you right then and keep their appointment. And, have the doctor talk you up to his patients so they can become yours too! Lots of insurance companies pay for massage when it is done at a chiropractors office, especially the Bureau of Workers' Compensation. I'm not sure what the laws are where you live, but in Ohio you have to become a preferred provider with the BWC to be paid for claims. I'm sure the doctor you work for accepts insurance, so he's probably set up already. If not, I would look into it. Trust me, it's worth your while money wise!
I wish you the best of luck!
Let us know how it goes.