Different products that can be used to weather your trains.
I've been collecting products to use with weathering over the years. Here's some of what I own, or have read about.
Chalks in this form, are dry powder, usually in stick form. Do not get these confused with the aforementioned weathering powders. Chalks are cheap, and can be about at just about any store that carries art supplies.
One issue with chalks, is they don't adhere well. You'll need to dull cote before, and after. They tend to disappear when dull cote is applied.
Weathering powders/chalks have a leg up on chalks. They're basically the same concept, though an adhesive is mixed into it, thus allowing the it to stick much better. I'd still recommend dull cote afterwords, to help it stay on the model.
PanPastel creates an art supply pastel chalk, in round trays, similar to powered makeup. Often used by canvus artists, it has a small amount of binder in it, and sticks well to dullcoated models. Used in conjunction with or replacing weathering powders.
See how I used PanPastel in conjunction with a liquid based rust product from AK Interactive here: Rusty Boxcar Roof with AK Interactive and PanPastel
Water Mixable Artists Oils/Gouache:
This is an interesting product! Its the same basic idea as an oil color, however its much more adapt to weathering. It is water mixable.
Model Trains Weathered was a great resource, I'd recommend visiting this YouTube video by armor modeler Michael Rinaldi: https://www.youtube.com/watch?v=oE_9XijaHP8
Oils are simple to use for "pitting" and "streaking". To make a rust pit that has streaked down the side of the car, a small dot of oil is applied using a #0, or equivalent brush. Let it start to set, then take a wider brush, wet it with water, or Micro Sol Decal Set and pull downwards from the dot, thus creating a streak.
Oils can also create much larger, thin washes of rust, or dirt, ect.
See how I used oils, and some powders to replicate a large rust spot on a boxcar door: Weathering an ExactRail Greenville Boxcar
This is where it gets interesting! You want to make a fairly thin wash with the gouache, make sure the area where you apply the color to the car is WET after applying. Now sprinkle some salt (normal table salt is fine) on the surface, the was should collect around the salt. Once dry, use your fingers to rub the salt off, and touch up with dabs of gouache to finish off the pits.
This can be used to seal chalks and powders. Combine a brush or sponge applicator dipping in hair spray prior to the powder to make a more textured finish.
For more on weathering, check out these books:
Weathering for Railway Modellers: Volume 1 - Locomotives and Rolling Stock
Done in a Day (Model Railroader's How-To Guides)
The Art of Weathering
©2008/2020, Josh Baakko, https://www.modelrailroadtips.com