Even if you're meticulously careful as you add the grout around your tiles, you will still leave a slight grout residue on the surface of your tile. This grout residue creates a haze over your newly installed tile's surface, reducing its shine and marring its general appearance. Before the grout haze dries, you should promptly remove it from tile. While many people might clean this residue off with a damp sponge, some types of tiles rip sponges apart. As an alternative, remove the residue using sawdust.
Add grout between your tiles as you would normally, and allow the grout lines to "set up" or harden enough for you to safely walk over.
Pour sawdust over areas where you think some grout residue remains, and then sprinkle the sawdust with water to slightly dampen the dust.
Rub the floor with the dampened sawdust to remove grout residue from the surface of the tiles. For smaller areas, use a burlap cloth. To clean grout from larger areas, use a push-broom with soft bristles.