Just back + b then forward.
How fast does the input have to be? I tried it, but I can't seem to duplicate the results.
Just to clarify, let's say you are facing right. So you press left on the control stick, hit B, and then immediately press right on the conrol stick right? And the desired effect is to do the side B facing right, but moving left?
I'm bad with examples, so sorry if you couldn't understand my question.
Also, if you do decide to change this to "the untapped potential of Marth's specials" then you should note that Marth's reverse up B is more usefull now. Marth turns around
before doing the up B now, so it hits behind him. This is actually really usefull for hitting opponents that like to land behind you with their aerials. Also note that Marth's up B has more recovery range than before. Even if you are too low to autosweetspot, you can still grab the ledge after the peak of you're up B.
As for down B stuff, I don't think there's really anything notable about it other than it being more usefull now that it does more damage. I think he might hit behind him now when countering the spacies' side B's (Ike did, but I haven't tried it with Marth).