I.  Oils

I use the Winton brand of artist's oil colors, primarily involving Raw Umber, Burnt Umber, Raw Sienna, Burnt Sienna, Titanium White, and Black.  I'd suggest starting with those primary weathering colors, and if you see some other rich brown that you'd like to try, by all means grab it!  1 tube of oil colors may last your lifetime, and it never seems to go bad.  One tube I use I purchased when I was 16 years old and it's still good (I'm 44 now, to put that in perspective)!  The above car used all these colors except white.  I also use a variety of brushes, including a sharply angled end brush, a very tiny bristled brush, and a 1.2" wide soft brush for most of my effects. 

The oils can be applied directly from the tube, or, if you plan on using a lot of the colors and doing more than one car or loco at a time, you can place a dab of each color on anything fairly non-porous to use as a pallette.  A piece of the thicker, scrap Masonite will work fine, for example.  Colors can be mixed to get the effect you are looking for, and I try to work from prototype photos to get a feel for that mix.  As you can see, as intense as the model was, the prototype was even worse!

PLCX 16364 Prototype Photo, Barstow Yard on Santa Fe

PLCX 16364 as shown in RailModel Journal
 

For the above car, the various rust colors were dabbed on in layers and gently blended, then given a final wash down the side of the car with the 1/2" brush slightly wet with mineral spirits to get a "rust washed downwards" look.  I was careful to avoid the area of the reporting marks, since that was to get a much lighter treatment.  After letting the model dry for several days until the odor of the oils was no longer evident, I gave the car a couple of coats of Testor's Dullcote straight from the aerosol can to protect what I'd already done, then used a lighter rust treatment and a bit more mineral spirits to produce the effect on just the reporting marks.  This also got a Dullcote sealer once dry. 

Several other very rusty cars will be added here as time permits.  I will also expand the section to include fading freight cars.  These will include the Athearn PS-5344 boxcars from the December and June 2001 issues of Railroad Model Craftsman, and the ex-PC X-72 boxcar which will appear this year in the June 2001 issue of Model Railroader. 
 

GT Atlas boxcar, faded with techniques described in January, 2001 Railroad Model Craftsman and rust techinques described above.  Click HERE to go to the Fading Freight Cars page.

II. Other Methods

Acrylic Paint-
I often use a combination of techniques to get an effect that I'm looking for.  When it comes to paint, I generally use Polyscale and some Model Flex paints for weathering.  The colors to get are 414329 Polyscale RR Tie Brown, 414323 Polyscale Rust, 414293 Zinc Chromate Primer, and Model Flex 16-172 Rust.  (While I'm at it, might as well recommend a good "grime" color, the always surprising Polyscale 414176, UP Harbor Mist Gray!)  I generally start with RR Tie Brown, and add some Rust to it, either brand (yes, I actually mix Polyscale and Model Flex!  Though they separate in storage, a quick shake and they're back together long enough to use.)  If I'm looking for a "new" rust, I might add just a bit of the Zinc Chromate Primer, but go easy, a little goes a long way here.  The two brands' rust colors are quite different from one another.

I try to never measure my mixing proportions, so that in service I get natural variations in the fleet.  I have over one thousand freight cars and over 250 engines, and all (if they are in service) have Kadee couplers and either Jay Bee or NWSL wheels that are painted some rust color variant.  These paints hand brush very well, and I often use a Paasche single action airbrush to do base rust coats on roofs and other parts. 

Weathering Powders-
Lots of folks use powdered chalks for weathering, but this has the disadvantage of either rubbing off, retaining fingerprints, or "going away" when clear-coated to protect it.  I've had great results with the weathering powders from Bragdon Enterprises (2960 Garden Tower Lane, Georgetown, CA 95634 530-333-1365).  Their powders have an adhesive component built into the powder itself, actuated by rubbing!  When stroked on with a brush and "massaged" into place, they stay put, and look good.  They also go a long way. 

If anyone has any comments or questions they can feel free to e-mail me at "miker@mrhobby.com".