Brush debris and dirt from the stairs with a broom.
Mix water and soap in a plastic bucket and work the solution into the stairs with a nylon-bristle brush. This will help remove oil and grease deposits and make the application of the sealant more effective.
Rinse off the porch stairs with a garden hose and then wait for the stairs to completely dry before continuing.
Stir the nonslip sealant and pour it into a paint tray.
Work a paint roller through the sealant so that it is evenly coated and then roll the sealant evenly onto the stairs in a thin coating. Roll in one direction to avoid leaving a textured pattern. Allow the sealant to dry for 48 hours before using the stairs.