weathering wooden bridges

[thebigj55]

In my high school wood shop class I am building a wooden bridge for my ho layout. the trusses look like this :http://www.modelersdepot.com/katons...-1-1-1-1-3-1-1-1-1-2-2-1-1-1-1-1-4-1-1-2.aspx

I want to weather it to age it a bit. what techniques can i use w/o an airbrush? what are the best products to use i have the tracks sitting on pine and the trusses are oak

 

[Cjcrescent]

Stain the wood before assembly. I would use an almost black stain to make the bridge "new". For an older one, use a progressively lighter, greyer stain to indicate an older bridge that the creosote has leeched out and the wood is more subjected to the elements.