Greenscreen - You're doing it wrong...
See what I mean? People... listen to me very carefully now. There is NO point in using a greenscreen for your picture, if you're going to leave little bits of green in it. It just looks weird, ok?
So, here's now you do this right! (I am sure there are lots of other ways to do it right too, but this is the way I've found fastest and easiest.)
1: Let's say you know you want to place the cutout pic on a dark backround. What you do first then, is two -identical- pictures, one with a green background, and one with a dark background. Preferably close to the tone of the background you're planning on using, but for a dark one, black works most of the time.
2: Place these two -identical- pictures in one document, one layer per pic. Make sure they're perfectly aligned.
3: Hide the black layer
4: Go to Select - Colour range
5: Use the colour picker on the green background, and set the fuzziness high. I usually go with 200.
6: Show the black layer again, make sure it's selected, and press delete. In other words, do NOT delete anything from the green layer. You don't need the green layer for anything aside from what I just explained. The green layer is evil. Rember that. Eeeeeeeviiiiil. We're only using it to reach our goal, then we ditch it.
7: Tadaaaa! Now you have a nearly perfect cutout, no green bits stuck in the hair, no need to manually erase any green junk at all. What the colour picker missed to grab, will not be green, but black, since we deleted from the black layer. Black is way less eyecatching than green, and my crazy flowy hair, is crazy without beeing green-crazy.
Bonus tip: If you're actually wearing things in this shade of green, use another colour! Make it a bluescreen or a redscreen or a fucking pinkscreen. I don't care. Just don't get bits of green stuck in your hair. Thanks.