The will does not require strengthening. It is entirely strong enough when it is being utilized regularly. What needs strengthening is the resolve to utilize your free will capabilities to choose to make decisions with more positive anticipated outcomes.
You are correct regarding mental discipline. Mental discipline is strengthened by the regular utilization of the 'genius, and more', capabilities of the intelligence one received at the moment of his or her creation.
You are entirely incorrect regarding Ouija boards. They are precisely what is chosen to be used by weak minds. hehehehehehe, I have one here on my desk as we speak, so to speak.