SD45 on Piru. Not completely happy with the weathering on the loco, but will keep trying. The overdone rust is just powders that have yet to be sealed so it can be changed or added to.
John, overdone is in the eye of the beholder. A little heavy up the sides, perhaps, but I think the effect on the horizontal part of the nose is great. And I think you'll also get some reduction of the effect with a shot of clear flat.
The rust was applied with Bragdon powders so can easily be removed, but if you think the matte over it will cut the effect I will do it. If I loose too much off the nose should I dust while the matte is still wet or simply re-apply after it dries?
I'd let it dry to be sure of how the effect looks. If you go easy on the matte you should be able to reapply as necessary without getting too heavy a clear coat, and I suspect that trying to apply powder to wet or tacky paint could be a recipe for disaster.