The 57-year-old, back with a second spell with the Glovers, has been telling his squad about the pain of play-off final defeat, having been 90 minutes away from the Premier League with Bristol City in 2008.
And Johnson is making sure his players are mentally right ahead of kick-off as they bid to avoid a repeat of that feeling.
"Brainwashing does sound illegal but what it is is having everyone thinking the same," he said. "They've got to be committed to the cause and behind the tactics and believe in them.
"There is no use going to war and not believing the cause and not sticking to the plan. You have to come away with a good experience, because the bad ones stay with you for the rest of your life.
"We do a lot of psychological things in the build-up and maybe after the final we will let you know. It is pretty heavy stuff on occasions and so far, so good."
Yet Johnson's pre-match plans were almost unravelled by his top scorer's driving ability earlier this week.
When 23-goal Paddy Madden was reversing from his parking space after training, he failed to realise Fulham loanee Dan Burn's leg was still outside the passenger door. But the damage was just a tyre mark up an angry team-mate's leg, much to the relief of their manager.
"The only problem we had is that Paddy Madden has just passed his test and he drove over Dan Burn's ankle which is unbelievable," he added.
"He nearly put our centre half out of action with a bad bit of driving."