Well, what i normally do is this:
Make a selection (doenst normally get all i want, we'll say of the mirror) with the magic wand tool.
Then i press q (for quick mask), and everything tht is red, is not in the selection.
I then press b (for brush), select the proper size with soft edges, and paint out what i want selected (that is, make it not-red)
If you are painting in red, press x, and then it will paint out the red.
Once that is done, press q again, then go layer, new adjustment layer, and curves (for brightening, darkening, and other good things). I normally take the center pt and move that.
i hope i explained that well enough, but ii found that is really easy for editing on section of the whole.
And, i use a new layer, so that if i dont like it, i can change it. IF it was on the background, i cannot go back the next day and change it.