First, make sure that the joints are free of dust, dirt or mortar residue. Now you can mix the grout. Make sure that you do not mix too much (approximately as much as you can use in 20 minutes). Now spread the grout with a suitable smoothing board. Once you have applied everything evenly, let the grout dry until it is matt. Next, rinse the joints. After 1 hour at the latest, you can then start cleaning the tiles and removing the film with a sponge board.