The best thing is to purchase a small grout removal tool. It is a tedious job if you are not planning on replacing the tile as well. You can go with a manual saw which is around $10. I would go this route rather than a power tool. Although it's more labor, there is less chance of breaking or scuffing the tile.
You are going to need safety glasses and an oscillating tool with a blade made for grout removal.
Also you want to vacuum as you go, that way you can see your progress.
With the tool, lightly press the blade into the grout, let the tool do the work. Go along either horizontally or vertically with the blade at a 90 degree angle. When you have removed as much as you can of the grout, you need to make a pass at an angle to get more of the grout out.
For the chunks and stubborn pieces you'll need a small tip carbide grout removal tool, be careful to not use it as a prying tool, it could chip your tile.
The final dig uses a dull utility knife blade.
How to Remove Grout
You can use a hand grout saw. You can try a flat tip screwdriver. Works on some grouts. A Dremel tool with grout removal adapter.
Hi Frances: Not a problem! Check this site for ideas:
Are you talking about old grout
Here is info on how to do this
If possible, I would try to have a few extra pieces of tile on hand if you decide to do this as some of the tiles may get damaged in the process. We've had that happen.
Hello. If it’s not an extensive job a manual grout saw might be considered. If it’s a large area you might want to use the motorized tool like a Dremel with a specific attachment head.I hope this helps.
Here is a video tutorial on how to remove grout: https://www.youtube.com/watch?v=A_CEJv5crHM
Heres a great vid to help you out https://www.youtube.com/watch?v=XzxbUrlPKh8
This may help: https://www.tipsbulletin.com/how-to-remove-grout/
This tool works well to remove grout: https://amzn.to/2Oa0few