Lee Turner, who I consider one of the greatest, if not the greatest, O scale weathering artists told me he uses everything on his models before he's done with them. Chalks, acrylics and oils and then sets them with some brand of dull coat paint.
That being said, I've used just about every brand of chalks and powders over the years, but quit using them about two years ago when I learned about Pan Pastels. Much, much finer pigment (Like women's pancake make-up) which adheres to the model much quicker and easier. Will it lighten when over coated with a clear coat...........yes...........but much less than most chalks. Fantastic for chalk, but only one component of the arsenal.
Here is an unfinished model using only Pan Pastels. It has not been over sprayed, but you'll have to rub hard to get in on you hands. Most likely won't set it as it really doesn't need it.
