Buffer beams get dirty. They're not alone in that, obviously, but this aspect of weathering doesn't always get the attention it deserves, and I include myself there.
There is much opportunity for detail weathering in O Gauge, so I decided to put a little more effort into this subject by applying a wash to the varied protruberances on the buffer beams. A straightforward process, involving a rigger brush, white spirit and MIG Dark Wash.
The brush bristles are first loaded with white spirit and then dipped into the bottle of wash. The tip of the brush is applied to the edge of a detail (bolt head in this case) and capillary action will take the fliud as far as the consistency permits. The thinner the wash the further it will travel. You should be able to see just where it has been applied by studying the photographs. Note that the colouring will be lighter once the wash has dried, as is always the case with the paints we apply to our models.