I received an email from a customer who purchased some of the weathering pigments I sell on Ebay, as linked below:
Shadow Grey weathering powder
The problem he had encountered was mimicking, that is weathering, the crusty dry cement found on cement wagons. I was asked if I could help out, so here we go! I should also point out he asked about dipping the wagons in real cement. I don't recommend this, as you have no control over where the cement goes and you may well just finish up with a wagon that looks like it's been dipped in wet cement.
The first thing is to build (or buy) your wagon. In this case I used an AR kits NPRX wagon with a Keiran Ryan Brass etch walkway kit which I then paint and decal. I used the gray primer as the finished colour plus a gloss coat for decals. I then dull coat the model and let it dry.
The next step is to brush paint some clear (water base) paint on the model where you want the crusty cement .
Then add the pigment by dropping it over the wet paint and shaking the loose powder off. Don't dab at it, just leave it to dry.
It may look thick but you can tone it down when dry by rubbing or picking at it until you have a realistic look.
I now use Extra hold hair spray over the model to blend the powders. I tone down the spotty patches by adding powder where needed, giving an even weathered apperance over the whole model.
Another layer of dull coat and some more powder work to finish off. I then weather the bogies, add the KD's, and it's ready to roll!
P.S. I will do my best to answer all your emails but please be patient some envolve a lot more work to get a blog post up with details and photos. Next I will show how to colour sand stone walls.