I'm not entirely sure myself, i believe you have to go DT as your move hits but like i said im not 100% I know it works with real impact, just go DT as the first hit connects then release DT as the final one connects and you should have hit them 5 times instead of 3, I'm not too sure on the other moves though when I try it I dont notice too much of a difference (at least not like with RI )
EDIT: sorry I got confused and thought you meant on the other Gilgamesh attacks also :\ well hope this helps ^_^ like i said though you can also distort other Gilgamesh moves, Im just not too sure on the timing