Grout Stain on Slate floor tiles.

Hi Everyone,
I have just undertaken laying my first tiled floor and although it went very well.. i didn't quite realise the importants of removing as much grout off the tile surface as poss before it dries.
I did manage to get most of it off but now it has dried there a small patches of grey grout smears. I tried using plasplugs cleaner and to an extent it shifted some but not all, can anybody reccomend maybe a stronger cleaner that won't stain the tiles itself and is it ok to use a wire brush or should i just carry on using the Plasplugs stuff over and over again and hope it moves it.???

Great forum by the way, just moved in a new place and visit here everyday now as most my spare time is spent decorating at the mo.

welcome your holyness

( i suppose you looked at it as Chris t)

Just the first six letters of my name (christopher).
Not been able to perform any miracles yet.. although how i got home saturday night after a few was pretty impressive.