Myself and a few friends were helping some other friends grout ceramic floor tile in their new home. This was my first time doing it and the ones who were applying the grout got a bit carried away and did it faster than those of us who were cleaning the wet grout off the tile could keep up. To make a long story short, the grout started drying faster than we could clean and now there is a lot of excess grout, both thin streaks and lumps of it that have dried on much of the tile. I believe it was a polymer based grout and we had to mix it ourselves. Now that it's dried, how can we remove the excess grout from the tiles?