I got to watch many cars being filled. The elevator was 1 1/2 blocks out of my back door. I saw MANY grain boxcars as well as covered hoppers being filled on the Pennsylvania RR spur behind the house. The hoppers were rare, mostly boxcars.
The elevator used lumber, not paper, when "patching" or bulkheading the door. The wood would fit into an iron bracket that was similar to the bracket on a barn door only much stouter and larger. There was always a pile of lumber along the tracks by the loading "chute". Actually it was a couple of long hoses connected to the side of the elevator.
I can remember, now, that a guy would actually get on the roof of the cars to fill them via a hatch in the roof. I'm wondering if they used old reefers? I've never seen cars like these. Another guy would get inside the car until it reached a certain level, climb out and finish filling the car. The car sat on a set of scales so that they wouldn't overload the thing. The scale plate is still there but the old wooden elevator burned down long ago.
I remember old Charlie George, the owner of the elevator, paying us boys a quarter to sweep out the cars before they were loaded. Then we would go into the office and buy pop and candy. Pop was 7 cents, with a penny deposit on the bottles, and the candy bars were a nickel as were potato chips. I guess he knew he'd get his money back in prompt order. We usually just sat down on the bench on the platform, just outside the office door, under the roof and enjoy the fruits of our labors, so bottle deposit was never charged.