I am going to cover the wood frame with styrene sheet. To do that, I'll be using contact cement, which is just nasty stuff. After the styrene sheet is on there, I am going to paint it with the metallic paint I found at Lowes.
So, I moved my operation to the garage. I suspect the building was made out of corrugated sheet metal, but I don't have large styrene sheets like that. Second, I figured the building will be 3 to 4 feet from the front of the layout, so the corrugations will not be visible. I found a sheet of Plastruct N-scale simulated wood board in my supply stash, so I glued it to the short wall (dark-gray). After the glue cured overnight, I used a razor blade to trim the sheet to match the profile of the wood structure.
I had bought some 24"x18" sheets of styrene at several thicknesses at a local hobby show, so they came in handy, as this building is 23 inches long at its maximum. Similar to the side wall, I glued a sheet of 0.020" thick styrene sheet to the long wall. After that cured, I trimmed it to fit the short wall's sheet, and the top and other edges. For the roof panel, I used 0.040" thick styrene (that's all I had left), but I wanted the roof to extend over the walls by a scale one foot. To attach this panel, I placed a lot of shish-kabob wooden skewers on the roof's contact cement, and using a scale one-foot wide piece of stripwood, lined the short side of the styrene sheet up with the short wall. Then, one by one I could remove the skewers and permanently attach the roof styrene sheet. A bit stressful, but it came out OK. It was then a matter of trimming all of the other sides and the roof peak to shape.
After I had built the wooden framework of the building, I placed it on the layout. It turns out that the second roof panel is not visible from the normal viewing angle. So, I didn't want to waste precious styrene on it. However, I did want to model the roof top, so I cut a two-foot strip of styrene, and clamped it to the first roof panel's styrene. Then used regular styrene cement to attach it.
I then delicately glued a second strip on the back roof panel. It took a bit of blue masking tape to get it into position and stay there while the styrene cement cured. On the wood side, I simply applied a bead of Aleene's Tacky glue, which should be enough to keep that strip in position.
With some delicate cutting and filing, I got rid of the excess material, and we have the final model built.
I then applied three coats of the paint to the model. The paint is meant to appear a bit blotchy, which I thought was a bit of a neat weathering effect. I am happy with the result, especially at a distance. The paint left a shiny surface, so I sprayed the whole model with a coat of Testors Dullcote. The model is now finished. I placed an Artistta S-scale figure next to it, so that it conveys the enormous size of the building.