Finally got to work on the sawmill project.  Finished up foundation for the load out structure.  The foundation was built up using 1/4" ply and bracing then covered with self adhesive brick paper.  The decking is hand cut Alder and perimeter bracing is Hickory.  The NBW castings are Grandtline.  I thought I would share my weathering technique for adding rust and grime.  I use acrylic chalks and alcohol.  I typically have a scrap block of wood and some strips of sandpaper kinda like artist mixing pallette.  Chalk is rubbed on sandpaper to get fine powder and colors can be mixed to get desired effect.  I dap brush in alcohol then dab chalk dust and apply to model.  The tone can be controlled with more or less alcohol.  For the NBW castings I drilled pilot holes and glued them in.  The wood rail was already weathered with brown and black chalks.  To rust up the castings I first dabbed them with the Folk Art Acrylic Rusted Pipe paint then made some rust powder.  The rust powder was made by mixing Red, Orange, Brown and Black chalk (keep mixture on darker side).  The castings were then dabbed with dry rust powder and same thing for streaks on the brick.  To add some grime I lightly dipped brush in alcohol and brushed out excess (brush should just barely be damp) dabbed brush with black chalk powder and lightly traced over rust streaks.  Be careful with Black a little bit is all you need.  Better to due multiple light applications than over doing it.  The decking was colored using Brown, Gray and Black chalks mixed then applied with alcohol.  After decking dryed it received a final wash of black to make joints and nail holes stand out.  To finish this project the foundation pieces will receive a coat of cheap hairspray to seal everything.  I hope this is helpful to someone.