Basilica of Saint Paul Outside the Walls
Schuster received his ordination as a priest on 19 March 1904 at the patriarchal Lateran Basilica in Rome from Cardinal Pietro Respighi (its archpriest). He returned to the Basilica of Saint Paul Outside the Walls in 1904. His two mentors during his time of education were Father Bonifacio Oslander and Tommaso Riccardi.