The stratergy of Mewtric is to get a turn 2 Disconnect lock using either Manetric Ex or Mew Ex. If need be, then you can use Mega Shot for a bench KO or Ex KO or something. Due to the small "core" Pokémon line needed, you can run a number of techs (like the version that won Worlds had Regirock Ex (Hl)). However, this deck also focused on disruptiong with Pow! Hand Extension. Since that was rotated out, people have been using Pokémon Reversal, but it isn't as good as it used to be.
Anyway, Mew Ex is a great tech in so many decks and can be used as the basis of a deck like Mewtric or Destiny, or the basis of a new rouge deck that you may like to make (I've seen someone use it with delta Deoxys, Persian (Hp), Gyarados (Hp) and Golduck (Hp) and did pretty well).
If you want to know any more, just ask and I hope I've helped!