Try out Dogwaffle! Honestly a great free program for all you artists trying to do some real art online, has tons of brushes and textures for drawing and simulating paintbrushes and such. There is a professional one you have to pay for, but the free one is great for your needs!
http://www.thebest3d.com/dogwaffle/free/
Sorry if someone has already mentioned this. I am lazy and don't pay attention.