Gimp Multilayer EXR import plugin
This plugin imports multilayer EXR images into GIMP. Please note that layers contained in the EXR image will be converted to tga format and therefore reduced to 8bit/channel. So, don't use this plugin if you want to import high-range (HDR) images into the gimp, but simply for importing multi-layer images such as exported by blender.
For this plugin to work, you also need the djv tools (djv-info and djv-convert) installed and correctly running on your system. See http://djv.sourceforge.net for info & download. To install the plugin, simply copy the file-exr.py file into your gimp plugins folder. It is tested on linux but should work on any platform.
The workflow you can achieve with this plugin is the following: When rendering an image in blender, you can divide the render into several render layers, specifying for example to render each blender layer in a different render layer. You then specify "multilayer" as the image format.
Then, after saving the image as an .exr file, just open it in gimp (gimp will now recognize the format) and all the layers will be imported as separated layers, for your painting convenience... Enjoy!
Example of the results here...