Which particular infinity buildings?
The lasercut MDF/HDF ones?
The not-lasercut foamed pvc sheet ones?
The lasercut stuff is easily painted without losing the detail, the etching is deep enough that unless you drown them in paint, it will still show up, as the unetched surfaces usually absorb more paint than the etched/cut areas.
I've used rattlecan AND airbrush, and both did the job. MDF/HDF WILL drink paint like water, though, so you should best seal it before using an airbrush on it, as you will go through paint.