How to color skin is one of my huge questions.

I know it deals with the color theory, but Ive never gotten around to studying it partially because I could never find a good article on teh interw3bs about it D:

plus all the tutorials I find are so goddamn vague.

Id like to be able to color hair/skin like these guys;
http://sketcher2007.deviantart.com/

http://aozorize.deviantart.com/
http://endling.deviantart.com/

But whenever I try and paint like that, ( I use Paint tool SAI) the skin colors always come out super over mixed, and like almost blurred together. It sucks and I dont get what I would like... D:

Is there a technique or something Im missing?