I watched the 'tutorial' for After Effects. Here are my comments:
It lasts 07:24 mins, but the information could have been given far quicker. To avoid having to say "sorry I am a bit tired", perhaps it should have been made when you were more awake! And all that wandering around the file selector window is not helpful. I don't like the line "green screened him out", it would be better to use a better term (i.e. Chroma keyed).
It may be wise to explain what version of AE is being used. Some versions include 'Keylight', which is probably better than using multiple Chroma Keys effects.
Might it be worth worth mentioning how garbage mattes can be used to help prevent the Key spilling into the subject.
However, the voice over was friendly, clear and confident with very few umms and aaahs.
TimS is correct, I was talking rubbish and my use of the word "spill" was unhelpful.
What I meant to say was that if there was any green areas which need not be keyed out, then perhaps they can be excluded from the effects of all those colour Keys. That may prevent some of the poke throughs which appear as holes in solid objects, and may help to retain some any of the natural greenness in the subject.