Ruins
Prime the terrain with Matt Black Undercoat
Using a large brush, basecoat the ruins with Khorne Red
Don't worry about being messy or getting a perfectly even coat, as black showing through will make it look better and add a weathered/aged look. Aditionally, don't spend a ton of time painting over things you know will be painted as a metalic.
Do a heavy dry brush with Wazdakka Red
Using Cadian Fleshtone do a final, lighter drybrush over the very tops and edges of the highest points.
Apply Gun Metal to all silver metalic details. This includes doors, floors, windows, lumen housings, ect.
Next, start to pick out pipes and similar pieces and paint them with True Copper . This step will likely require two coats.
Use Black Legion to cover all the cables, wires and tubes- Apply sacred washes Nuln Oil for silver, Cryptek Armourshade Gloss for coppers