Ah, it makes much more sense now. I can see why this system would take a long time, its really cool! Being able to swap characters without one of them dying first was also fun.
It was kinda hard, but I managed to do a combo with a normal attack and 2 skills. I think if I wait until I see the bar, its already too late to press more than 3 keys, so it takes a bit of memorizing when the bar will pop up if you want to do the more advanced skills.