Edit: November 22th, 2016
I wanted to take November to rest a bit and put all this stuff in order but.. it was not possible.
I managed to finish a new version, the one which I use, and to upload a super ugly video showing functionalities.
There is no need to append any node group now, you do not need to manage with the node viewport and if you careful it should work fine.
Anyway there are some things (like saving udims textures all in once) which are not tested yet, so use this taking that in mind.
See the ugly video here: https://www.youtube.com/watch?v=YJYa...ature=youtu.be
Here is a new and provitional link. I would like to use git but I have no idea how to send this to blender managers. (and I had no time to have a chat on irc)
some weeks ago I worked in this addon which allows me use Blender as a nicer texture painter. I created a UI to work with layers and it mimics some features from other softwares like Photoshop (layers, mask, adjustment layers..).
Also, which is more interesting, I can paint a model with a UDIM - Multi Tile uv mapping, where the uv mapping is distributed in several tiles out from 0 to 1 uv coordinates. This system is commonly used to paint high detailed textures, splitting the model in several parts and use many smaller textures rather than one super big texture.
It is not hard to use, but it uses some new concepts, so I wanted to share it in case anyone wants test it and tell me how difficult is to understand. I have created a getting starter tutorial and a quick video about the workflow.
Download from here