Photoshop :: Coloring And Matching Skin Color

I'm working with 2 pictures of people. My goal is to replace the face-parts (lips, eyes etc.) with each other.

So person 1 will get the mouth of person 2, and backwards. pretty simple, as all I have to do is match the skin color, and from now - piece of cake. (I actually said piece of cake :P )

So, what I normally use are only 2 tools: Hue/Saturation, and Color Balance.

Problem is - it's still pretty difficult to get perfect results. and beyond that, sometimes I just can't manage to get to even a normal solution. so it's very frustrating.

My question is: What are all the tools that are used to match colors?

(Until now, what I basically did is: take the slider, move left - check if better. if not: move right - check if better, if not: return to center. like this with each slider of the 2 tools I mentioned above. doesn't sound very professional, huh?)

P.S. A reference to even a bunch of tutorials and guides about coloring, would mean THE WORLD to me, as around 60% of my Photoshop are coloring and stuff like that.