The styrene is basically Evergreen sheet. For the wings, I just cut the shape of the wing an sanded it to shape For the wing joints, I glued stretched sprue over the wing and then sanded it. I scribed the control surfaces with a No. 11 blade.
The fuselage was a bit more problematic – I have a set of line drawings for the Catalina with cross sections, so cut layers of plastic sheet then laminated them together to gt the rough shape, then sanded and filed until I was reasonably close. I took the canopy from a 1/350 Trumpeter B-25 (from their USS Hornet kit), and the ball turret in the nose is a clear plastic bead from a McDonald's Beanie Baby knock-off (my dog got to it and chewed it up, thousands of little clear plastic spheres everywhere).
The Quonset hut was quite simple to make...I cut two circles from Evergreen corrugated plastic, and cut them in half. I took thin plastic sheet and glue it to the semi-circular disks, then trimmed the bottom half and flat sanded. I sprayed it gray, drew the panel lines with a #2 pencil, then used dark gray pastels over the pencil lines to simulate the edges of the sheet metal.
Any good hobby shop, especially those that are heavy into model railroading, will have all sorts of materials you can use. The boxes, crates and pallets are all N-gauge accessories. Basically, a box is universal scale...a small box in N-gauge (1/160) is a big box in 1/350. Since most aircraft components come in large crates, it's easy to scale things out.
Jeff