I believe that butcher paper is waxed on one side.
These days when I store trains, I put them in food grade plastic bags. The bags are left open, and sometimes I even make extra holes to prevent any moisture from becoming trapped.
The train (in the bag) is then placed in an individual cardboard box.
Baseball card storage boxes are good for many items, otherwise I use boxes that I purchased from ULine.
I would also consider using corrugated wrap.
In the past, I would wrap the train (in the bag) in newspaper. for some cushioning.
I've never put desiccant right in the boxes with my trains.
While I prefer not to store any train items in the attic, I do keep some stuff up there because I don't have another spot. I had boxes of Lionel "O" gauge track, including Postwar 022 switches up there for years, just stored in plain cardboard cartons. Much to my surprise, none of the track has developed any rust. I imagine that other people's results would vary, depending on the climate, and how their attic space is ventilated.