For those who might not already know, you can get one of the most powerful compositing tools for free.

It's not a demo version. It has a slightly reduced feature set, but you probably won't need those capabilities.

Fusion 8: You can get it from Blackmagic Design.

At a time when Adobe charges a monthly fee to use its software, Blackmagic Design is literally giving away the competition for After Effects.

Included is perhaps one of the best greenscreen keying plugins, Primatte.

Check it out.

https://www.blackmagicdesign.com/products/fusion

But wait, there's more.

Also available is DaVinci Resolve 12. A full-featured color grading program, with editing capabilities.

Same low price: Free.

There's a "studio" version that might be worth looking at for the additional capabilities.

https://www.blackmagicdesign.com/products/davinciresolve