Drive-in any protruding screw heads you come across.
Make three or four scoring passes, then snap the backer over a 2×4. When all the pieces have been laid out, label them and set them aside. When the grout is dry, all that should be left on the tile surface is a thin and weak haze that you should be able to wipe off with a moist sponge. If the haze is difficult to remove, use a grout haze remover on it.
