Dick Francis, for example, knows all about horses; he writes books about horse racing, horse transportation, horse trainers, etc. He does not pilot his own plane, yet he has written several books where he (or the hero) is a pilot. Dick Francis obviously knows how to research. If Mince researched enough, he could write about being a train driver OR a passenger.
Coo, this is all a bit deep. To put things into perspective (I think), refer to Beau introducing readers into Book 6:
"....I thought it was time to explain how my two chroniclers set about their business. To capture the flavour of my life in the Legion, months of research are needed. To make my visits to the pub authentic, the lads (Roger, writer, and Andrew,artist) forced themselves to spend hours at a time in hundreds of bars throughout the country.
"It was a terrible sacrifice," said Roger, "but one we felt necessary".
Andrew agreed. "It was hell. Sometimes after hours of research, we could hardly stand".
To learn about the desert, Roger looked at a postcard of Morocco.........."
