Let me say this right off the bat: no, I'm not painting anything. A few years ago I built a PRR A6b and, and at the end of the post I threw in this "weathered" version: I wasn't that happy with it, but I wasn't too interested at the time, and I decided I'd look at it later.  Well, now is later!   Almost all LEGO train models are built with the assumption that the locos or cars are clean and well-kept, but this is really the exception in practice. I've seen LEGO weathering done a handful of times, but I don't feel like I've ever seen it done that well. At the same time, I don't feel like it should be that hard. So after studying some photos of real weathered locomotives, I gave it another go: Here is my U30B in black:   This first weathered sample is supposed to suggest dirty with a little bit of wear. The photo exemplifies the pattern I see on such locomotives: the uneven application of dust and grime almost forms a gradient where the lower half is darker/lighter than the upper half (depending on the base color), and this gradient is largely what I'm trying to depict. I think the trick is to strike the right balance between intentional and random - I want the bottom to be primarily grey (dirty) and the top primarily black, but then I need to randomly reduce the number of grey parts as I move toward clean areas of the loco in order to suggest that gradient:   This second sample is supposed to suggest rusty less than dirty. This photo is of course of a model, and I think the rust is a little aggressive, but another pattern emerges: the rust is much more evenly distributed across the body but still comes in large patches without clearly defined borders. One of the difficulties in both attempts, but more so in this one is trying to balance resolution with features: I wanted to preserve the panels and such that texture the body of the locomotive, but at the same time I wanted to break up the panels such that I wasn't making entire panels "rusty" at a time.   This final sample for now is based on a Conrail N6A transfer caboose I'm working on. The "clean" model is as shown:   The weathered model is more of a blend of dirty and rusty. I specifically wanted to weather this model because I could get a lot of "drawing" resolution with 1x1 plates due to the caboose's simple construction. Again, I'm largely trying to make a gradient between the trucks and the body, but I've thrown in some rust spots as well.    Overall I'm fairly happy with all three results, but I wanted to get some second opinions. Are the weathered variants any good? Is it too distracting? Maybe most crucially, does anyone think the weathered variants look better than the clean variants? I'm almost certainly going to built one of these in brick to explore what it actually looks like, but any thoughts are appreciated.