Adobe After Effects CS6 Question (I Need Help)

hey guys I’m new to this forum but I feel seeing as I’m interested in Video Editing I feel I need somewhere like this to discuss further knowledge with you guys. So any way my question is that, Have you ever seen the effect where there might be a BMX clip of someone ramping really high in the sky and is twixtor to slow down and they some how mask the BMX rider out so they can speed the up the sky I think it makes for a really nice contrast between the sky and the rider so my question is, Is there any tutorials on how to do this or is it quite rare out of all edits I have seen that is the only one I have seen.

via Video Editing Forums: Digital Director – Adobe Premiere, Premiere Elements, and After Effects