Thanks grj,
I think it is important for the smoke unit to keep an eye on smoke production.
Since I've had the BB and the Lionchief+ B&O, I can tell when smoke is waning and then, after cooldown, add more fluid. Still experimenting with the doseage as not to overfill. But, for the BB, I will start using 1/3 of a MegaSteam dropper.
However, the Berkshire junior that came with the Polar Express set smokes as much as the BB and goes a long time - one heck of a little engine!
RickM46
And now it starts.