After you have formed and poured your new concrete walls you will need to apply a finish to the surface to help seal it and to make it more visually appealing. A popular, easy-to-apply and long-lasting finish is called "rubbing." When you rub out a new concrete wall you are applying a thin coat of Portland cement and literally rubbing it with a sponge float to create an attractive and durable finish. It will take a few tries to get the feel for doing it right, but then you will be surprised how easy and fast it is to do.
Grind smooth any drips or bumps of concrete left on the wall. You want the surface to be as flat and clean as possible. Wipe the dust from grinding off with a dry brush before going on to the next step.
Fill one bucket halfway with water. This will be used for cleaning off your tools.
Mix a slurry that is three parts Portland cement to one part water in the other bucket. You will want the slurry to have the consistency of pancake batter and will want to hand mix the water and cement with a mixing trowel to maintain the best control over the mix.
Scoop a small amount of the slurry mix out and put it on the middle of the blade of the Mason's trowel. Apply the slurry to your new concrete wall by holding the trowel blade to the wall so the slurry is pressed onto it and wiping the slurry across the wall with a smooth arcing motion. Evenly coat a 2-by-2-foot area; this is a good size area to work in so the drying of the slurry does not go faster then your ability to rub out the wall.
Watch the slurry on the wall. When it begins to dry (a light gray color appearing on its surface) take your rubber float and gently begin to rub it in circles across the surface of the drying slurry. You will see a circular pattern begin to appear and the smooth surface of the applied slurry will change to a gritty, sandy one. This is how you want your finish to appear. Continue rubbing until you have covered all of the applied slurry, then repeat these steps. Make sure you clean your tools in your cleaning water before each application.