Hello,
I have recently constucted a small industrial layout and I want to see if you guys have any tips on how to weather modern locomotives and rolling stock. I don’t know what color paints and powders to use and what brand. And how do I take the sheen of new plastic off a new car. My fleet consists of an Athearn Genensis BNSF WFE reffer, and Athearn Genesis Southern Pacific boxcar, an Atlas CN&W boxcar, an Atlas BN boxcar, an Atlas CLC centerbeam, and Athearn RTR UP covered hopper, an Atheran RTR CSX gondola, and Atheran RTR CSX Boxcar, a Walthers Proto ULTX Terra tank car, a Bachman CP Rail cylindrical hopper, an Athearn RTR scrap gondola, an Athearn RTR CSX gondola and an Intermountain BNSF covered hopper. My only locomotive is a Athearn RTR CN SD40.
I see you posted this question twice (in slightly different forms).
This topic has been covered quite a bit on these forums, you should use the “search this community” function, as well as the web in general.
I will say: dullcoat (or equivalent) to remove the sheen on the rolling stock, and also to provide a base for better powder weathering. Light powder weathering to start, then you need to look at protoype images to see how far to take the weathering. Also good is airbrushing with very thin washes of dark brown and light greys (I believe Mr. Seoborg uses this method). After adding weathering powders, seal with a light overspray of dullcoat. For a modern era layout (post 1980), consider graffiti decals for freight cars with large flat surfaces like Gondolas, Boxcars, and Covered hoppers.
That said, again there are hundreds of different techniques discsussed on this forum, many for very specific types of effects. Peruse prototype images, find examples close to what you want, and then search for notes on how to achieve that look (e.g. extremely rusted and worn steel gondola; light weathering of almost new ARMN refrigerator car, and so on).
The double repost was my mistake and thanks for the advice.