The technique is really easy. It uses one characteristic from itr/kind: 8: the itr causes objects to move to the centerpoint of any Type0-bdy it hits. The character who can use this shield-move has a unique bdy in a lot of frames (in the example it's at y: 1000). The shield is given an itr/kind: 8 at y: 1000 and the position is corrected every TU, independent from wait and the timer. Now you just have to set the defense itrs and you're done...
Have fun ^_^