Did my first tile and grout clean a couple of weeks back,was impressed with the results,as was the person who booked me.
I used aqua mix heavy duty tile and grout cleaner,this was possibly a bit overkill chemical wise,as they were also not in bad condition,I just wanted to make the best first impression.
I used a rotary with a bristle brush,it was one I hired,and I think the brush was probably for polishing,rather than cleaning,but it did a good job,and the payment paid for my recon Victor europa.
I brushed the diluted chemical on,scrubbed for a bit,mopped it up,then rinsed it off,grout all came up white when it dried,and looked great.
As it was my first one I went in at .26p per sq ft,will be upping this to around .40p per sq ft ,once I have been trained,and have more experience