The frame dirt has now been airbrushed onto the frames as well, taking some care not to get overspray onto the body. This is not critical, but it helps to keep extra work to a minimum if I decide to spray the bodywork a significantly different shade of filth. With the locomotive upside down in the cradle, it is quite easy to ensure that the underneath of the running plate is covered. The accuracy of the airbrush also helps to keep unwanted paint off the wheel treads.