I think the main thing is to experiment and find what you're comfortable with. Although I haven't used white glue, I done something almost the same as what you are suggesting but with a flat acrylic to work as a binder, and I was quite happy with the results. I found that with multiple coats, I could generate a very heavy build-up if desired. With a small brush, you can put the slurry into corners just where dirt and mud would collect in real life.
I recently did kind of odd technique that actually worked surprisingly well. I sprayed a pastel dust/flat acrylic mixture through my airbrush, to give a light dust effect, and was reasonably pleased with the result. I had to open up the airbrush a bit more than normal to prevent clogging, but since it is an inexpensive single action unit that I ise for clear coats, I don't think that I was truly abusing the airbrush.