__I finally found a great tutorial on Greenscreening, however I've got a thick dark line around...

I give the tutorial a C-. Keylight is now much improved and for most footage, you don't need the other two effects. I've only done about 2 keys in my life that required only using clip white and clip black to clean up the key. I also rarely use Screen Matte, but if I do, it's only for the first pass at cleaning up the matte. 

The reason you have a thick dark line around your key is that you have not tweaked enough of the settings. 

Always start with a garbage matte. As soon as you pick your key color switch to Combined matte and take a look at the matte you are generating. Start by adjusting Screen Gain and Screen Balance, then tweak clip black and white. Now move on to all of the other controls in the Screen matte section. To pull a really clean matte from a very well shot 10 bit or better footage from a professional camera like a Red or an Arri Alexa is going to require you to fiddle with about 1/3 of the controls. If it's footage from a consumer camera, you'll need to tweak about half of them. If it's footage from your mobile device, you are going to need to tweak most of the controls to get a clean professional looking result and it still won't be as good as it would be if you had professionally shot footage. 

Key Cleaner is kind of a last resort sledgehammer and Spill Suppressor is easily outclassed by Keylight's edge correction tools unless you really need to hammer on the edges. I cannot think of the last time I used either of those tools, but then again, I almost always work with 10 bit or better log footage from professional cameras.