I vacillate, when it comes to grout. Sometimes it's que sera, sera, and sometimes it's all-out war: baking soda, hydrogen peroxide, OxiClean, toothbrushes, grout brushes, elbow grease, and five million moppings to clean the residue with fans to speed drying times in between rounds. But ever since I've discovered this completely awesome way of cleaning grout, I almost look forward to doing it, and really, it's another kind of life-changing magic.
Here's the secret: magic erasers! I know there are grout pens out there that whiten grout, but that's just paint. I want to actually clean my grout. Magic erasers get the job done, and they do it quickly and relatively painlessly.
Technique-wise, I usually cut my standard size magic eraser in half, wet it to slightly more than damp, and scrub the grout line as I squeeze gently. I find that the wetness seems to help loosen the dirt. I swipe with a dry rag and move on to the next line.
The caveat is that the grout will totally eat through your magic erasers—and those things aren't cheap. Proper magic erasers are great, but Scrub Buddies from Dollar Tree have worked almost as well for me.
Here are some others I plan on trying: