He added: "I know people don't believe that. I guess they have trouble believing that somebody who's been in the limelight for so long is anxious not to be in the limelight."
He is making an exception to advocate for the presidential candidacy of his younger brother, Jeb Bush, a former governor of Florida.
"He'd be a marvelous candidate if he chooses to do so. He doesn't need my counsel 'cause he knows what it is, which is, 'run,'" Bush said.
Painting now occupies part of every one of the former president's days, and is giving him an opportunity to "keep learning in life," he said.
"Painting has changed my life in an unbelievably positive way," he said.
The Bushes became grandparents for the first time just this month when their daughter, Jenna Bush Hager, delivered a daughter, Mila. Asked what he wants to be called by his grandchildren, the former president joked, "El Jefe" -- Spanish for "the chief" or "the boss."
"I will tell you this, holding that little child was one of the great joys of my life," he said. "Holding little Mila was unbelievably pleasurable. And I'm looking -- I really am looking forward to this new phase of our lives, which is being a grandfather. ... I plan on spoiling the child."
Family will be on Bush's mind Thursday as well. His father, George H.W. Bush, now 88 and in frail health, will be among the former presidents in attendance. In a courtyard at the museum, there's a statue of the 43rd president side-by-side with his father, the 41st.
"He's meant a lot to me in my life," the younger Bush said. "I wouldn't be sitting here without his unconditional love. And it gives me great comfort to know that he will be by my side for eternity."