Step into the effect and mark in/out for both the Fill and the matte channels. Then copy to the clip board (“c” on the keyboard), open the clipboard (ctrl-3 for the tool pallete) and edit these onto the timeline in the same order (matte over fill), you may have to add a new track here, then make the move that you want on one of them.
Drag this effect icon from the effect editor to the bin and apply it to the other clip.
Finally go to the effects pallete and Alt drag the “Matte key” effect onto the top clip. Once you are happy I suggest collapsing these down to one track (over the background track), marking in/out and subclipping it over to a bin.
In a similar vein, did you know that you can get cool effects by replacing the contents of the fill channel with vision?
Cheers
David Mcsween
Editor ABC Brisbane, Australia