There is too much thinset in between my mosaic shower floor tiles (in some spots it looks like grout). What do I do before grouting?
You need to remove the thinset by grinding it out, otherwise you'll end up with uneven coloring in your grout. Thinset is also stiffer than grout, and the added rigidity could cause your tiles to crack in the future. You'd be best off biting the bullet and grinding it out now rather than replacing the tile entirely later!