What are the best techniques for effectively using a grout pen white to refresh the appearance of grout lines in a tiled surface?

To effectively use a grout pen white to refresh grout lines in tiles, start by cleaning the surface thoroughly. Shake the pen well and apply the white ink along the grout lines in a steady and even manner. Wipe off any excess ink immediately with a damp cloth. Allow the ink to dry completely before using the tiled surface.