As you know, Hunter, I'm entirely self-taught in Photoshop and through years of efforts and headaches have achieved the skills of a smart 4th grader, but I can tell you what I do in that case:
Zoom in on the element you want to move, make a Path using the Pen Tool with plenty of points to get the nooks and crannies, convert it to a Selection and use the Move Tool to, uh, move it to the other image.
Always make sure the resolutions of both documents match, so you're not surprised by a change in the size of the element when you move it to another document.
Is this what you were talking about or is it too basic? One thing that I've learned about Photoshop is there's always several very different ways of doing something.