Take note at a couple of parameters in After Effects that you may forget when chroma keying in Keylight...
Screen Pre Blur- use this after adjusting your screen matte, in the video he uses a setting of 2 and it helps to "feather" the edges through blurring.
Screen Shrink/Grow- use this to get remove the soft green edge around your subject, the video uses a setting of -3.5, (*negative* because you need to take the green out) but this is determined on a case-by-case basis.
And most importantly to get a good chroma keying result- use the eye dropper as close to your subject as possible!
Best of luck with your keying.
