Your concrete countertops are generally ground and polished wet using a professional diamond grinder. Follow the following tips to use a wet grinder or polisher quite effectively:
You have to keep the surface even: Avoid using a wet grinder such as the high-speed metal grinder. While using wet concrete grinders, press the whole face of the grinding disc or wheel evenly against your concrete surface. In this way, the disc will work evenly and the concrete will not be gouged. Care has to taken as if you are grinding with just the outer edge of the disc touching the concrete, it will wear out the rim of the disc thus creating crescent shaped gouges in your concrete surface.
Avoid using too much pressure: Just remember that grinding with diamonds does not require much pressure. Apply just that much pressure suffice to hold the grinding disc flat against the concrete countertops. If the disc will spin fast, then it will grind faster.
Using the right amount of water: Plenty of water is require by diamonds to cool the disc as well as to flush cuttings away. Too much water will cause a mess, similarly too little causes excessive tooling wear.