Question: How to scrub grout clean.
Option 0: In a bucket, mix vinegar and water in equal parts.  Using a brush, dip it in the mixture and wipe down the grout in a grid fashion in order to ensure equal coverage and time spent without missing a spot.
Option 1: In a bucket, mix vinegar and water in equal parts.  Pour this mixture into a spray bottle and use it to spray down the grout by gently squeezing the trigger.  Let sit for 5 minutes and wipe away with a brush.
Answer: 1