Read the Mewtwo card more carefully because you can only put that energy on
Mewtwo. But here are two different approachs to your method.

1. Keep doing Energy Absorbtion and drain your discard pile of Fire energy.
Then Retreat Mewtwo and Mr. Fuji him. This means more energy for your deck.
(Use Defenders or Potions)

2.  Use Fossil Gastly and keep doing Energy conversion with your occasional
Potion. Power up Charizard/Ninetails/Arcanine along the way.