I am lookin for a good way to make a rust wash for buildings to get the effect of rust stains/streaks that come from pipes and other metal things on the sides of buildings. I’m also looking for a good way to make spotty surface rust like that on corrigated meatl roofs and building sides.
Thanks
I’ve had really good luck using chalks for weathering a “rust wash” down the sides of buildings (and rail cars) as you described.
One other product you may want to look at is “Rust-All.” I just purchased some, and it makes very convincing rust spots on metals (I believe the product is real rust dissolved in alcohol). I rusted up a plate girder bridge with the stuff, and it turned out very convincing. If you apply it and let it dry several times, it gets bumpy, which adds to the realism.
I would try Rustall. It was very effective for me when I used it for the same purpose. T would also give Modelflex’s Rust and Great Northern Orange for the roof.
I’ve also used RustAll with some success. My only complaint with it was that on some white gons I was weathering it turned them pink instead of rusty. Some dilute India ink dealt with that problem! 
Clear tracks.
Al D., Rail Baron
White Bear Lake & Northern RR
“Making Tracks Across Minnesota”
http://www.geocities.com/wblnrr
Try dry brushing for the effects of rusty streaks from leaky pipes and other things that might create a rust stain (or any other stain far as that goes). I’ve had great luck using that technique with a mix of Floquil Rust and Roof Brown (Polly S works too). I just finished (this morning) a corrugated metal roof. After getting the color of the roof right with aluminum, grimy black, and roof brown, I did a rust wahat worked out great. I use Floquil paints. To get the wash I touched the tip of my bruo the lid (Floquil Rust) then dipped it in thinner (di sol) and let it run down the roof. It came out as I hoped it would.
Larry n VA
This was dug up from page 588. Anyone know where I can source “RustAll”?
Fergie