Dress in clothing that covers your arms, legs and feet completely. Wear gloves, safety goggles and a paper mask or respirator.
Scrape away any loose paint from the porch floor using a putty knife.
Mix two parts of water and one part of heavy-duty commercial detergent in a bucket. Dip a long-handled, stiff-bristled brush into this solution and scrub the porch down with it to remove dirt, dust, grease, oil and other debris.
Fill a power washer with plain water and choose a setting that is easy for you to control. Rinse the porch floor thoroughly, starting at one end of the porch and moving to the other, using an even, steady movement. Allow the porch to completely dry.
Pour the concrete coating paint into a large paint pan or other reservoir. Load a long-handled paint roller with the paint and apply a thin, even coat to the entire porch floor. Allow this coat to dry for an hour, then apply a second coat in the same manner. Let the porch dry for at least 24 hours before using it.