Pale Background paintings

during a previous tutorial I was told to try and create more depth with my city-scapes. I felt the best way to do this was to paint the backgrounds and foregrounds seperately, as with other images when painted together I always seemed to make a mistake, of the ink would bleed. Although the ink bleed looked interesting, it was not exactly what i was looking for.
I felt that by painting each individual layer separately, I would be able to scan them into photoshop and layer them via the computer. This would give me more room for mistakes and also i can play with darker and lighter contrasts.