Manuel F. Ayau was actively involved in the formation of the National Securities Exchange and the Guatemalan Chamber of Industry. His business interests included cotton and rice cultivation and he established the largest factory of ceramic tiles in Central America.
Ayau was the author of several Spanish-language books: El proceso económico; Cómo mejorar el nivel de vida; De Robinson a Viernes; La década perdida; No tenemos que seguir siendo pobres para siempre; and El comercio. He also wrote both English and Spanish editions of Not a Zero-Sum Game. For many years he had weekly columns in local newspapers and his articles have been published in the Wall Street Journal, the Freeman and other well-known publications.