To avoid damaging the grout, opt for a medium-bristle nylon brush, not a hard steel one. Simply spray warm water on the grout ...

With a stiff-bristled brush or a grout brush, scrub the grout lines vigorously in a circular motion. Never use abrasive sponges or steel wool. They'll scratch tiles. Rinse down any vertical ...

or stainless steel. I used a broom to do a quick sweep of my bathroom to remove dust, hair, and debris. Then I squirted Zep directly onto all the grout lines, no brush needed at that point.