Johnston -- who fathered 10-month-old son Tripp with Sarah Palin's 18-year-old daughter, Bristol -- plans to strip down for the shoot in "early November," Jones says.
Johnston isn't nervous about showing all.
"He's pumped. He's ready to shock the world! The hell with fifteen minutes," Jones tells Us. "As a matter of fact, when I picked him up, he came out of the house naked. I said, 'Not now!'"
Adds Johnston: "I just get naked. That's what I do."
Jones didn't reveal how much Johnston was paid for the shoot (The "New York Post" reports he received six figures) and swears: "This is not about the money. I don't remember how much it is. It's a little bread."
The same month Johnston shoots his pictorial hits the web (Playgirl is an online-only magazine), Sarah Palin is due to appear on "The Oprah Winfrey Show."