Brass collected plant specimens for the Queensland Herbarium from the 1930s to the 1960s, as well as participating in several international expeditions to New Guinea, the Solomon Islands and Africa.
From 1939 to 1966 Brass was an associate curator of the Archbold Expedition collections with the American Museum of Natural History.
He was associated with the Archbold Biological Station at Lake Placid, Florida, for which he helped to formulate the organizational structure it has today, and also where he lived between expeditions.
Brass was director of field operations for an expedition in 1949–50 to tropical Africa, sponsored by the Upjohn and Penick companies, to find precursors for the manufacture of cortisone.
Brass retired from the American Museum of Natural History in 1966 and returned to Australia, where he died at Cairns, Queensland in 1971.