._. Sorry if I'm kind of necroing a dead thread; but I happen to have quite a fair amount of information on this topic. I'm replying in hope that this may help someone else, if I am already too late.
Green Screen editing can be done in various ways; it all depends on what software you have access to. In general though, for adding in various video effects, you're best bet is probably Adobe After Effects. After Effects is usually for adding in various video effects to a production after the general timeline editing, as such it is mostly used in conjunction with video editing software such as Adobe Premiere or Final Cut (Mac only).
If you work with both After Effects and Premiere you have the added bonus of being able to import and export your work between After Effects and Premiere almost seamlessly. Premiere carries some of special effects that After Effects has; including Chroma Key (Green Screen). It's a little more difficult to do on Final Cut though, but in my opinion, Final Cut is a better video editing software.
I'm getting off track. ._. Back to the point; I suggest After Effects and/or Premiere if you're somewhat experienced with video editing. After Effects and Premiere can be incredibly difficult and frustrating if you don't know how to them.
An alternative to After Effects and/or Premiere would be using Adobe Photoshop. You may be able to use Corel PhotoPaint, but once again file compatability and support can be an issue. You could edit each frame individually, removing the green (or whatever colour you choose to be your negative space) manually. There are plenty of tutorials on how to
do Chroma Key in Photoshop. Here are the first two results I got from google:
http://www.youtube.com/watch?v=sAF9GFBTaAohttp://www.youtube.com/watch?v=mQCUP2WbSiQHope that helps.