Make hair in Blender Internal, but render in Cycle, realistic skin in blender render? Even though I have made a character and applied material and some lightning effect, I still can't get somewhat skinny color - somewhat red as like real one.

In this video by Andrew Price, the object is not so real, but when rendered it gives very realistic image!

And I want to make hair for my character. I found every one using Cycles. But when I do Cycles render it takes forever, about half an hour for an image. So I want to make hair in Cycles and later choose Blender Internal. What will happen if I do so?
Assuming you don't change any of the particle settings, then there would be no problem rendering the hair in cycles and blender internal. Note you will need two different materials, one for the internal, and one for cycles.
See this question for how to use materials in blender internal and cycles.