Well the grout removal tool was good, but the teeth have worn down after 1 floor and several scrubbing. I guess that's normal.
Big problem now is cleaning the tiles after grouting. It's taking forever to clean and takes about 6 scrubbing sessions. I've left it half hour to touch dry but then there's that much grout all over place it takes a lot of scrubbing. May be I'm catching the grout in the tiles and wiping it back on to the tile?
But its uncaliberated slate and not a smooth tile so excess grout hides everywhere! It's a nightmare!
Taken 2 hours to clean it off 2 sqM