Open the primer and pour it into the pan to a depth of about 2 inches.
Roll the roller into the primer and apply it to the wall using an up-and-down motion. Make sure that the primer is going on in an even coat.
Dip the paintbrush into the primer. Apply it to any areas that the roller did not reach. This will be the areas closest to the ceiling and along the baseboards and corners. Allow the primer to dry overnight.
Discard the paint roller from the roller tool and replace it with a new roller. Clean the roller pan.
Pour paint into the roller pan. Roll the roller into the paint and apply the paint to the wall in the same manner as the primer. Use the paintbrush to cover the areas the roller did not reach.