To echo luvdemtrains, thanks for starting this thread Randy!! Your two weathering projects for the club in Red Lion look terrific!!
Luvdemtrains - your boxcar weathering work is superb!!
Rob Leese - got love those grimmey Friscos. Wonderful job!!
Sitka - Your girder bridge wears your weathering well!! Looks like it's been out in the elements for many decades. Great job!!
One of my early weathering projects was the MTH coil car back in 2018. I first sprayed a coat of Testor's Dullcote ... let it dry ... then lightly sprayed a bit of Floquil Grimmey Black here and there.
Next I used gray pastel chalk to give it that "been in a dusty region " look ... I also applied rust pastel chalk along the some of the sill areas and some parts of the lifting bars. My process for applying the pastel chalk was to make a short chalk line then rub the chalk in a circular motion with my fingers. For hard to get at areas, I used a small paint brush creating circular motions with the brush.
Once I got the car to look the way I wanted it, I applied another coat of Testor's Dullcote to seal pastel chalks.
Incidentally I purchased this car at York from the MTH Parts Booth. For some reason there were some Premier freight cars on a table with a sign that read" make an offer". Mike Wolf was standing there and I made him an offer of $20.00. He accepted. I should have asked him to sign the box .... oh well. 
