Thank you so much. I have been watching so many speedpaints and tutorials to find how other people accomplish this but not one of them explained this move. Now that I think about it, it might be too obvious for those who are so used to PS to remember to explain the technique.
To avoid overdoing the selection, use the Ctrl Shift C command, then put the pointer over the underbase layers thumbnail (if you have one for the dragons head) and hold Alt + Shift then click. You'll notice your pointer turns into a select icon with a X in it. this means it'll only select the cross section between your over selection and the underbase.
probably late, but I noticed messing with the layer setting might sometimes give the effect you want. (you know where it says normal in the scroll bar, just click one at the time until you find a good one, and you'll have it memorized for later