The earliest case of spray painting applied to railway work was been described by the prominent railway journalist Angus Sinclair, who visited a Southern Pacific engine house near San Francisco late in the 1880s that was in the process of spray painting. He was told that the scheme would next be applied to freight cars." White, The American Railroad Passenger Car, Part 2, p447.
"A box car has been spray-painted by one 54-cent man [spray painter] in 15 minutes, wheras it would take a 72-cent man [brush painter] about four hours to apply the paint with a brush. The relative amounts of paint used are 9 and 11 gallons." 1922, Editorial: Paint spraying in railroad shops. Railway Age, 1922, Vol. 72, No. 11: 724.