Clean off the surface of the football using acetone or denatured alcohol. Ensure that the surface area is clean and dry, and free from any dirt or debris. Ensure that the football is fully inflated, as well.
Scuff the area that you wish to paint, using abrasive paper. The slick leather surface needs to be scuffed for paint to properly penetrate and absorb.
Stencil your design onto the football, using a thin black marker. The design, and where you place it, is according to your personal preference.
Apply painter's tape to the area surrounding your stencil. This will keep paint from running down the football and creating a mess.
Dilute 1 part acrylic paint with 1 part water. Note to use your background color for this step. Blot the scuffed area with the diluted paint, using a sponge. This will create a surface area that paint will easily adhere to. Allow the paint to dry for a few hours.
Paint the design using outdoor acrylic paint. When applying the paint, use a flat, soft bristle paintbrush making even strokes. Allow the first coat of paint to dry for a few hours, then apply a second coat to give rich color. Ensure that you paint background colors first and allow the paint to dry before applying more paint.
Spray the dry design with two coats of clear-coat finish. Allow the first coat to dry thoroughly prior to applying the second coat. This will help protect the design. Remove the painter's tape carefully and enjoy your customized football.