i am kinda overhelmed with the radiosity function in blender2.26.
since i am used to have an independent gi or a ao based on raytracing i never needed to seperate the model after it.
i see the advantage of this having a vertex paint solution but all the other settigns in blender are like big ??? for me!
get yafray at www.yafray.org and there’s a link to yaBle the exporter for blender as well! have fun with it!
Here is a thread that shows how to use textures with radiosity, using dotblend’s method I find that I often don’t have to seperate the meshes afterwards. https://blenderartists.org/forum/viewtopic.php?t=3981&highlight=radiosity
Hope this helps some.