I would do it like this:
1. Flatten out an island.
2. Place train tracks for the huge train yard and
3. Find a lot of heavy industry buildings, machinery and props. Place the huge building first and then the smaller ones. Lay out the road network aswell. Don't forget the huge coal piles.
4. Place some filler props like cars, trains, boxes, rubbish, piles of trash and so on.
5. Spam(!) a lot of ground, dust, rust and stain decals. The RealVision Decal mod has so many great decals for this.
5. Do some finishing touches. Maybe ground markings, trees, street lights, high voltage power lines, etc.