Shortly after earning his black belt, Mattos accepted a professional opportunity that brought him home: a position as personal pilot for the Governor of Rio Grande do Sul. Relocating to Porto Alegre, the state capital, he balanced his aviation career with a determined effort to establish Jiu-Jitsu as a serious discipline in the region.
In 1992, he opened his first academy under the name Equipe Walter Mattos Jiu Jitsu, laying the groundwork for what would become one of southern Brazil's most important BJJ institutions. The following year, in 1993, Ze Mario Sperry — then a purple belt — arrived in Porto Alegre on the recommendation of Carlson Gracie, seeking out Mattos for training. Mattos recognized Sperry's competitive drive and potential, promoted him to brown belt, and brought him on as an assistant coach.
The growing significance of their partnership was soon reflected in the academy's identity. The team was renamed Equipe Walter Mattos/Zé Mario Sperry Jiu Jitsu before adopting, in 1994, the name by which it would become widely known: Sul Jiu Jitsu. Under that banner, Mattos and Sperry built a program that grew into one of the defining forces of BJJ in southern Brazil.