Using a damp cloth, wipe the tiles and grout to remove all moisture and surface dust and dirt.
Put on the ventilation mask, eye protection and rubber gloves. Spray the grout cleaner on the affected areas and let it sit for the time specified on the pack.
Using a scrubbing brush and a bucket of water, scrub at the grout to remove any dirt. Dip brush into the water to help the scrubbing process.
Shake the grout pen before use. Using the grout pen, follow the line of the grout to go over all the grout.