Step one for any Indirect Lighting/Global Illumination render is to enclose the scene and all your lighting in a polygonal environment.  If you don't want to do this, most of the light will just vanish off into space.

Reason for your renders stalling is probably transmapped hair.  The more complex the hair model, the worse this will be.  It isn't limited to just hair, but hair models tend to provoke this problem in the worst way.  A workaround is to hide the hair from raytracing - this isn't ideal, but it's better than waiting a month for your render to finish.  This is a problem that occurs in pretty much all GI render applications, when dealing with complex geometry that is partially transparent or partially hidden by alpha.

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