A common request you find is people asking to have someones head replaced by another. Here I show you how to seamlessly, professionally and realistically replace a head.
True I wish they made that more clear. In tool options you can select the source... However I find it easiest to just hold ctrl down, and the pointer changes to select the source. Make sure the right layer is selected for that. Then make sure the destination layer is selected (usually it's just the same later) and paint as usual
