I am not sure if it will work for you, but try the Roughen Edges effect.
Increase the border size, decrease the edge sharpness to zero, and increase the scale. That might do the trick.
Life would be easier if the garbage matte had a feather parameter.
Honestly, this is probably better done in After Effects using the Rotobrush tool.
That did the trick!! Thank you very much.
Steven, I was looking for some tricks to achieve the same. And this Roughen Edge thing works well. Thanks! I learn something everyday here.