Ideally you want to create a proper UV layout for your model before you rig it. Here is a way to create UVs after skinning/binding your model
Procedural Mountain Building
In this series of 3 videos I show how to procedurally build and texture a mountain in Autodesk Maya, using the texture deformer and simple node networks.
3D Paint Tool
These two videos show the basics of using the 3D paint tool in Maya, and how to then refine the result in Adobe Photoshop. The model used was created by Naeem Green ’22 A rather old but still useful tutorial can be found on 3dtutorialzone.com