In July, 1774 Father Fustér was transferred as supernumerary to the Mission San Gabriel Arcángel, registering his first baptisms at that station on December 28. Father Fustér replaced Father Gregório Amúrrio at Mission San Juan Capistrano in late 1779; after laboring there for over eight years, he accompanied Father Joseph Arroita to the recently established Mission La Purísima Concepción. The padre resided at La Purísima a mere two years, however, for he returned to San Juan Capistrano where he remained until his death on September 8, 1800. Father Fustér's remains were transferred to the "Great Stone Church" on September 9, 1806.