you'll get the hang of it, don't mash your buttons. start with simple moves like streak or helm breaker then move onto the simple combos. I think i've spent more than 8 hours in the demo trying to gasp the timings and now in the full game i have no problems doing rev on any move. But honestly, once you get the timing down it becomes second nature, you'll rev everytime you push the slash button.
I've spent so much time on nero that once i switched to dante i felt that he was very weak, that's just wrong lol.