zbrush does the job for painting on 3d models and texturing your 3d models as well. Like Kbade said there is a demo version available. @ www.zbrush.com. For texturing there is a script that can be downloaded within the demo called texturemaster. The textureMaster script is composed of 5-chapter tutorial on texturing, ranging from the basics to advanced concepts. Also included are tips on importing objects, creating morph targets, and working with UV coordinates. Also if you have downloaded the demo, check the zscript window palette (left of the interface) there are serveral scripts that can be loaded...like modeling, painting and texturing. Hope it helps :-)