County fairs offer a few different opportunities for the magician. The best will be as a paid performer. County fairs are always looking for entertainment for the fair. Sure they bring in the big name country singers, the demolation derbies and horse racing. These things fill the stands, but a walk-around magician or clown also adds to the fair enviroment.
Contact the local fair director and ask about their entertainment needs. You may book to do a family show and /or walk-around. Vendors in the vendors building are always concerned with foot traffic. I have been to fairs where the fair grounds are packed. People come in for the evening's entertainment, ride a few rides, eat some cotton candy and go home. The only way they will be in the vendor's building is if it is raining or they need to use the restroom. This is a real problem for fair organizers. They want their vendors coming back year after year.
Be the problem solver. Suggest the fair hire you to do walk-around in the vendors building. Of course the fair will need to advertise that you will be there, in their brochure and by a few well placed signs around the fairgrounds. This will bring kids and their parents into the vendor barn and this will in turn help the vendors. You may also be able to make a few good contacts for trade shows.
Of course, several hours of walk-around can be very draining. How much better it will be if the fair will allow you to set up a small stage area, and you do a 15 minute show every hour, or just two or three half hour shows each day.
If you strike out at getting hired by the fair, ask for a free booth. You will perform close-up magic, and sell a inexpensive tricks to the fairgoers. You could also do a small show and pass a hat much like a street magician. Why should the fair give you a free booth? Because in exchange for the booth, you are entertaining their customers and adding to the fair experience.