Paint Tool SAI is a simple painting and editing software when compared with other similar software available in the market, making it easy to use. What Is Paint Tool SAI Software Used for? Therefore, if you are looking for software that does not slow down your personal computer as such, then you can keep an eye on this option. Now onto the matter of the Paint tool SAI Brushes. It is a smaller program which means it does not occupy a lot of space in your device’s memory, unlike Photoshop which is a much heavier software and needs a lot of space. Paint Tool SAI is a concise painting and graphics editing software that is created for Microsoft Windows users.