Strategy for Catching Xerneas

I've beaten all the main stages up to this point (up to level 190 - Steelix at the time of this writing) and I still can't even complete EX18 - Xerneas, much less catch him. I want to get Xerneas so I can get Yveltal so I can get Mewtwo. Steelix was really hard for me to beat and I didn't catch him so I only have Mega Mawile, Nidoking, Nidoqueen, and Bronzong.

Is there some strategy I'm missing? Should I just grind levels on this team until I can beat it or should I catch Steelix first? Will I certainly need more gold or can I beat it without powerups if I get lucky?

Solution 1:

The only strategy is to use Mega Mawile and quickly destroy the ice barriers in order to free the grid from disruptions. I suggest you not to waste any gold on Expert levels (although MegaStart could be useful).

EDIT: Home buffering was removed in a recent update. You can no longer press the home button while playing a timed stage.

Your team is good, and I don't think you need to catch Steelix, its base power is the same as Nidoking and Nidoqueen.

If your team is at least at level 6 you should be able to beat it. It's kinda hard to catch it, I've always ended it with few seconds left, and I've caught it on my umpteenth try, with a incredible luck, at 1%.
Just don't give up.