I would start with a blob of greenstuff, then get in into the rough shape you want it. After that start pushing into it in the direction you want the hair to fall. Then to make sure you add depth roll out some sausages and place them about the initial blob in the same direction as the lines you made initially. (not really necessary per se but I think it looks better this way) Then leave to cure. After its cured, mix up some greenstuff with either magic sculpt or brown stuff for some added stiffness roll out sausages and place them where you want the flailing strands to be.
For the spikey hair, start out with the blob and then you can either use thin wire to position the spikes and then let cure. Or just make the blob with a greenstuff mix with magic sculpt or brown stuff and make the blob thick enough that you will be able to push in the spikes. Later you can cut and sand to taste if you dont get it perfect before you leave it to cure.
Those are my thoughts, though they might be hard to understand without pictures. I will try to find something for ya.
EDIT: Here is a good example of the first method except they use sculpey instead of greenstuff.
http://www.polymerclayfan.com/sculpting-hair.htm
