Try using madmax's Zenith lighting systems(available in freestuff, I think),......either the Hi-Res or Studio quality,........these give the most beautiful softness to shadows  I have ever seen(depending on the angle of the light),.........however, if you use these in conjunction with Premium settings, expect those 28 hours to turn into 60 or 70 hour renders. Sometimes I just use a radial light with soft shadows enabled(in the light lab) which will increase rendertimes but not as much as the Zenith systems. Hope this helps.

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