Put on the breathing mask before beginning any sanding work; concrete dust can be harmful when inhaled.
Equip the orbital palm sander with the 60-grit sand paper; refer to the orbital sander owner's manual for operating instructions.
Turn on the sander using its switch. Sand the entire surface of the concrete countertop twice or until the surface is notably lighter in color. (This may take several sheets of sandpaper.)
Repeat step 3, using 120-grit sandpaper instead of 60-grit sandpaper.
Brush as much concrete dust from the countertop as possible using the masonry brush.
Lightly scrub the surface of the countertop using the large sponge soaked with clean water. Rinse as necessary.
Evenly apply a coat of new concrete stain using a paint brush. Apply additional coats until the desired shade of color is achieved. Refer to the stain packaging for any additional application instructions.
Allow the concrete stain to fully dry before moving on. Refer to the stain packaging for drying times, as this may vary per product.
Evenly apply a coat of concrete sealer to the countertop with a paint brush. Apply additional coats as directed on the sealer packaging.