The Timer Ball is twice as strong as the Ultra Ball after waiting 30+ turns. Therefore, the Timer Ball is the preferred option. You can simply recover stall Mewtwo, which will leave it unable to recover by the 30 turn mark. Then, False Swipe it down to 1HP, put it to sleep, and chuck Timer Balls.Now, i caught this on my sixth ultra ball.
Sleep powder is most likely the best move to use so it cannot use recover, then lob ultraballs like your life depended on it. I'd reccomend bringing about 50 ultraballs.
Yeah that's a good tactic. Just throw out your HM slave or something as a scapegoat. XDYou can catch Marowak's on Victory Road with False Swipe
And a Substitute will work great here, so it can take the hit when it wake up so you can put it to sleep again.