How to Grout Uneven Tile
Clean the lines between the tiles and any thin mortar, dirt or other debris tiles.It is important that the grouting should be applied to a clean surface, otherwise it may not be set properly.If your grouting mixture pack recommends you spray the tiles with water before applying the grout, do so now.
Dig out a large mass of mud with your spatula and put it on the tile.Keep the grouting plane at an angle of about 30 degrees and use it to disperse the grouting into the cracks between the tiles.Use your finger to press the grouting into any space where the grouting plane is not filled with grouting.
Repeat steps 3 to 6 until you have applied the mud on all the tiles.Allow grouting to dry during the recommended time on the package--About 10 minutes.-Then wet your grout sponge and use it to wipe the excess grout from the surface of the tile.
Due to the uneven nature of the tiles, this will require several passes