It is like any kind of exercise, you need to start slow and build up. eventually the bubble will be automatic and will take almost no energy to maintain.

<hands him a large orb like device, and a bar of chocolate>

This is a telepathic damper, if you put it next to your bed it will stop you accidentally ending up in someone elses mind while you sleep. It isnt very effective for shutting out stronger talent but as yours is new it should do the trick. And don't forget you need to eat after every practice, you will need to replenish protein and sugars