Just think you should have simplified it for the member.
When I do wetrooms, shower cubicles etc its the grout that needs the attention, the tiles if they are ceramic or porcelain need very little cleaning, a power tool is complete overkill and it wont touch the grout < unless its flush > using a spray on Alkaline cleaner works well for me most of the time, scrub it , anyone who has a Hybrid Power washer hand held or similar will get a result as well, < keep the psi down a bit though >
Rinse with water and dry with a heat gun, then re-seal when its fully dry, if you havent got a power tool dont sweat it use a Nail brush instead for the grout.
If the grout doesnt clean to well < and some dont > then try a grout colourant instead of sealing it.
Regards Russell at Tile Doctor