Remove all items from the countertop's surface. Open windows in and around the kitchen for ventilation.
Fill a bucket with warm water and add 1 cup of TSP cleaner. Use a scrubbing pad and a sponge to thoroughly clean the counters. Rinse the countertop with fresh water to ensure no film is left behind. Allow the countertop to dry for at least an hour. Sand the countertop lightly with medium-grit sandpaper to rough up the surface for better paint adhesion.
Cut the nozzle of a tube of caulk at a 45-degree angle with a utility knife. Poke the foil at the bottom of the nozzle with the metal rod on the caulk gun. Place the tube in the caulk gun and push the plunger into the back. Turn the plunger 180 degrees then press the release button. Apply a bead of caulk in any cracks along the counter where it meets the wall.
Place painter's tape along the edge of the countertop where it meets the wall and any other areas that you don't want to paint. Shake a can of countertop paint thoroughly to mix it then pry open the lid with a flat head screwdriver.
Cut in around the perimeter of the countertop with a 2-inch paintbrush. Use the paintbrush to paint the edge of the countertop and other areas that are too small for a paint roller.
Pour some of the paint into a paint roller pan and submerge a 4-inch sponge roller into the paint. Start at the back of the countertop and work your way forward so that you aren't going over the wet paint. Roll the paint onto the countertop evenly with smooth strokes. Keep the roller loaded with paint by rolling it frequently in the pan.
Allow the paint to dry overnight then apply a second coat to ensure a proper finish. After the second coat dries, the countertop is ready to use.