It's not a normal ISJR because you need a platform for it to work. You have to do a down B and hold the analog stick diagonal down, BUT theres a sweet spot that makes it work, and it's the closest/soonest time you can do a fall through down B. You don't have to jump or press anything after the down B to make it work... It is still really annoying even though i know where the sweet spot is, i have trouble doing it continuously . My record is 5 times in a row, doesn't sound like much but it is..... 5 years later and still finding new stuff
Guide: http://www.youtube.com/watch?v=4Dq1sYNAwg8
Guide: http://www.youtube.com/watch?v=4Dq1sYNAwg8