This is a multi-building farm with stone walls and slate roofs. The STL’s are available here: https://cults3d.com/:1947056.
A very similar but not identical farm build is detailed by “Storm of Steel” here: https://youtu.be/umlfubM83-Y?si=A3jWVUSzHIA2qILR. The main difference is that his has brick buildings where this one is made of stone walls.
Prime white, then base coat in Celestra Grey
Pick out random stones in various shades of brown and grey. Dawnstone and Mechanicus Standard Grey
XV-88
Skrag Brown
Doombull Brown
Balor Brown
Mechanicus Standard Grey
Dawnstone
Apply a wash of Agrax Earthshade over all the stonework to unify it.
Paint the woodwork in green Warboss Green
Paint the tile roofs in Mechanicus Standard Grey
Highlight the woodwork with a dry brush of a lighter green and dry brush the tiles with Dawnstone
Apply the same stone painting technique to HO scale embossed plasticard mounted on a thicker plasticard base for strength.
Weather the tile roofs with Green Ochre , German Fieldgrey WWII , and Buff as described in the video.