The train only needs one cargo wagon.
Base station will load enough acid for exactly one wagon full of uranium ore.
Outpost station will only turn on when there is zero acid in the buffer chest, or 2000+ uranium ore. Outposts that don't need a train will be shut off, allowing you to name all outposts identically and only set two train stops on the train schedule. (Main - Uranium and Mine - Uranium)
I usually set my train schedules for 2 seconds of inactivity at each stop. However, I'd recommend the Main station's wait condition to be...
- Item Count -> Cargo Uranium ore = 0
- AND Item Count -> Cargo Sulfuric acid barrel >= 40
This way it won't leave if you're overstocked on uranium ore or if there's no acid production. Less fuel wasted on unnecessary trips.
1 train wagon = 2000 uranium ore, which needs 40 barrels sulfuric acid (2000 acid) to mine.
Unfortunately with the return barrels taking up a few slots, most likely there will only be 1800 uranium ore returning on each trip.
I personally don't use barrels, but they do allow you to just use one cargo wagon. If you fueled this train with nuclear fuel, it would get to the outposts insanely fast.
... and it will likely kill you multiple times.
Update: I originally forgot to handle empty barrels.