A lot of professionals use Photoshop to paint. I think it's really good, too. Painter 12 is great with the realistic brushes. And you can still use Paint Tool Sai on Mac. You can buy bootcamp and use it. OR, if you don't want to spend any money at all for Photoshop, Painter 12 and Bootcamp, you can always just torrent it. I found a free Paint tool sai for mac. But I don't really use it much. So I don't know quite well if I am equipped with everything for this Paint tool sai version of mac.