How it‘s done

Because I‘ve been asked many times. This is how I do it. 
(hint: if you open the picture in a new tab you can enlarge it and actually see something)

1 the idea still in my brain
2 the first scribble in the note book
3 doing the outlines of the windows with my awesome stencil
4 actually drawing the whole thing
5 adding some black with various pencils
6 scanning
7 'colouring' on Photoshop, working with 2 layers
8 adding the text and logo

There you go!