Cleaning grout on a tile floor

I read on Science Man that you could clean grout with SG non-chlorine bleach. It could be applied in several ways. I used a toothbrush to apply, waited a minute, and used the brush to scrub. I did wipe down with clean water to avoid getting bleach on adjacent carpet. We live in the country and the grout was really stained. Regular mopping didn't help. This method was AMAZING.