If you are not concerned with the aesthetics of the overspray and whatnot, there really is no issue. The densifier will really soak into the substrate around tiny little imperfections like what you are talking about. Picture a dry, dry cutting board that is in desperate need of a good oiling. Imagine you get out some good mineral oil and soak it down to let it sit overnight. The fact that there is a minuscule drop of dried food on it won't matter. That wood fiber will pull the oil in right around it. Now, if you have half a ham sandwich sitting on it, different story. The concrete will behave similarly. As long as we are talking about, say, dime size bits, I would say you are fine. I'm sure someone here will tell you to grind it for two weeks to remove the top inch but I have worked with this product (Ghostshield) and you are going to be fine.
