The following information will assist you in applying for jobs with Fairfax County. You may also download this helpful brochure to assist you.Fairfax County's applicant pools are very large and highly competitive. Need help drafting a job offer letter? She got handed a one page letter stating she is being offered a job as a teacher contingent upon meeting some conditions such as passing background check. Negotiating is as simple as asking a question. Many employers will negotiate to find a mutually agreeable salary and benefits package. New applicants can apply online to be a substitute teacher or substitute instructional assistant through the FCPS Instructional Talent Gateway. Fairfax County Career Pages. Welcome to the Fairfax County's job class specifications!