It's theoretically possible that, if you were to weigh literally thousands of packs to choose your heavy favorites, and bought hundreds of them, you might get a slightly higher pull rate of rare cards than if you bought the same number of random packs - but I don't recommend it, for two main reasons: Most game stores don't permit you to weigh individual booster packs before buying them - mostly because it takes a long time and holds up the line
Aleister the Invoker effect, add Invocation from deck to hand
Go heavy on self-mill and Surveil to dump your heavy-hitters into the graveyard, then tap Xu-Ifit to bring them back for free
ISBN 1-56619-950-6 Parlett, David (2008), The Penguin Book of Card Games , London: Penguin, ISBN 978-0-141-03787-5 Phillips, Hubert (1957), ed
Now, you can simply add Mew EX by taking out an Item card like Potion or even give up one Mewtwo EX for Mew EX