Clean the surface that is going to be painted. A cleaning solution can be purchased from any home building center; Red Max or any concrete and masonry cleaner will do fine. Spray the cleaner from a pump canister or spray bottle onto the surface of the slurry.
Rinse off the area with a power washer or garden hose, to remove any loose dirt and grit. Allow the surface to dry. If you do not want to use excess water for dirt removal, use a broom or brush to clean loose dirt out of the area.
Prime the surface, using a sealer to block out moisture and protect the slurry. Allow time for the surface area to dry. The product that you purchased should tell you drying times in the instructions.
Use a lightweight grout to fill in cracks, if the area has crevices and cracks that you do not want to show through in the paint work.
Roll the paint onto the surface area and let it dry. Alternatively, you can brush the paint onto the area.
Look over the area after the paint has dried to make sure that the paint covered the whole surface and did not leave any unpainted spots. If there are unpainted spots, you should repaint. Generally, every paint job needs two top coats of paint.