Updated 11/12/2021:
As Col. John "Hannibal" Smith of the A-Team would say: "I love it when a plan comes together!"
The smoke generator arrived a day ago, I hooked it up to 12VDC, positioned a PVC "smokestack" over it and viola! Instant air pollution, 1950's style.
Then I turned opened the window, positioned the duct work correctly and turned on the fan.
We've got serious airflow out of the train room through the basement window.
I'm declaring victory and moving on to other areas.
More when I know it,
George