Get your hands on the 3DS version with a friend. It's a 1v1 setup, but 3DS connection play was super-laggy the whole time in my experience. Either way, you have a Waiting Room where you have to press a certain input to start the match with someone else. If you don't do the L+R+Start (or whatever it is), you can practice and mess around as much as you'd like on the Sandbag.
If you want to have any enjoyment/learn anything from it, just mess with the Sandbag with a friend who also wants to learn about the characters (and therefore would do the same instead of starting the match). From what I've heard, they don't really police the 3DSes very much (and they didn't at my Best Buy), so you could get some quality time to feel out a character and his/her moves. We all want as much data as possible to talk about, so help us out here!
If you want to have any enjoyment/learn anything from it, just mess with the Sandbag with a friend who also wants to learn about the characters (and therefore would do the same instead of starting the match). From what I've heard, they don't really police the 3DSes very much (and they didn't at my Best Buy), so you could get some quality time to feel out a character and his/her moves. We all want as much data as possible to talk about, so help us out here!