Q - Okay, we've learned to read the directions more carefully. But we need to know how to remove all the excess grout that we didn't wipe off after an hour. We've been chipping at it with a razor blade. Some grout is a cement material which is mixed with water. Other grouts are mixed with a 'latex milk'.
Some grouts are more like an epoxy.
If so, you will need to identify this material too. These folks are usually the best sources of information regarding problems like yours. Be very careful with this, and any other chemical washes. You will have to protect yourself and some of the other surfaces around the tile e.g. tubs, faucets, floors etc. You should also find out what needs to be done to neutralize the chemicals you use.