Tracking with the Tracer
            is done using the same method as with regular garbage masks. See 
                     Animating Masks Using Tracking.
         
         NoteWhen animating selected
               vertices with the Stabilizer, the vertices do the tracking, not
               the pickers. Once you obtain the tracking data, you will need to
               go back through your clip from frame 1 onwards, making adjustments to
               the pickers where necessary.