I have started to paint the rails. But running out of the old and proven Floquil Grimy Black, and since no more of that is to be had, I had to find a suitable substitute. I went for Vallejo acrylic Model Color, #168 Black grey. A little darker than the grimy black perhaps, but it will do fine.
This is just a first step. Dirt and rust will follow so the unpainted spots, which can be seen in the picture, do not matter at this point. Also, there is paint on the rail tops which I will remove later.