In 1923, Trompf began designing confectionery boxes and wrappings for Giles & Richards, a Melbourne firm of commercial artists, before setting up his own studio in Little Collins Street, painting and designing thousands of advertising posters, usually of 25 x 40 inches (64 x 102 cm) format, and 24-sheet advertising hoardings, for which Trompf supervised all stages of production, including the lithographic printing.