I don't think anybody does job fair prep; however, the information you get from interview prep would likely be more than enough for a job fair.

That said, I am very against job fairs. There is nothing but anecdotal evidence on both sides of the fence to prove or disprove they have any influence in getting hired: Jonny over here went to a job fair and got hired by airline X, it MUST have been the job fair. Tommy went to 3 job fairs, none of those airlines called but instead got hired by airline Y that wasn't even present. Job fairs are crap.

I went to 3. From my perspective it appeared that the organizer was making money hand over fist. The airlines making billions in profits got a free pre-interview, and the guys with the least money were the ones footing the bill. It just felt wrong to me.