You have to use the reaction commands for them too.
You have to do the last attack in a limit to get experience. Doesn't matter if the last attack hits and enemy or not I think. Easiest and fastest one to use will be Sonic Blade because it uses less MP than the rest.
You have to use the specials, check the shortcut menu when you're in Limit form(the one that usually has your spells or whatever you assign) and then use whichever of the 4 attacks Limit form gives you, then press Triangle for a while because you need to do a full special, each one of these gives you one point of xp for Limit form. You don't even have to hit anyone, but you have to be in battle mode.
Thanks all..gah why is this not explained in game