Bill and Professor Oak are to get through your deck in a quicker fashion than normal, getting to what you need. Make sure to use cards you won't mind missing to pay for its cost. Energy Removal keeps an opponent's Pok mon down while you lay down the assault, thought using it on your opponent's active Pok mon while Mewtwo is fighting for you is counter-productive. Finally, Gust of Wind is to ensure that your opponent won't get away with sending damaged Pok mon out of harm's way by sending them to the bench. There are a couple of things you will need to look out for when making and playing Psychic Assault.
Trading cards is one of the best solutions to fill out the requirements for the deck.
When playing the deck, be careful against Psychic Pok mon, as all your Pok mon are weak against Psychic. The up side here is that you have Psychic Pok mon as well in the deck, so an opponent who uses a lot of Psychic Pok mon will face the same difficulties as you. Finally, make sure you use your trainer cards to their maximum effectiveness. For example, don't use an Energy Removal on a Pok mon you are about to knock out anyway. It is better saved on a Pok mon that has some energy attached to it on the bench or on an active Pok mon that you aren't going to be able to knock out right away.