Leather can be used as a substrate for painting with various art materials, including acrylics, oils, watercolors, and drawing media. However, it's essential to prepare the surface by cleaning and removing any coatings or waxes. Golden Artist Colors recommends using acrylics, specifically the Fluid Acrylics/GAC 900 combination, for painting on leather, as it provides a uniform application and can be adjusted for opacity. The addition of GAC 900 can also add flexibility and a softer feel to the paint, depending on the type of leather used. It's crucial to test the paint and substrate combination before starting a project to ensure the desired outcome and durability. (Source IDs: 2, 5, 7, 9)