Dip your toothbrush or grout brush in the paste and work it into the grout. Spray the area with your vinegar + water solution. The vinegar will cause the baking soda to bubble up and will start to work away that nasty soap scum. Use your brush and get all the way into the grout lines to remove buildup. Sweep or vacuum your glazed tile floors regularly to keep them from getting dull.Tiles may be resistant to dirt, but sand and grit can dull glazed surfaces. Clean tilewith mild detergent and clean water, using a rag or chamois-type mop rather than a sponge mop.