When influential comedian Garry Shandling died two years ago, he was remembered as both a top standup comic and the creator of two of the most innovative sitcoms in television history: "It's Garry Shandling's Show" and "The Larry Sanders Show." 

Now, Shandling is the subject of the new documentary "The Zen Diaries of Garry Shandling," by fellow comedian and film director Judd Apatow. Apatow had incredible access to his hugely successful but highly insecure subject, including Shandling's personal journals, 목포콜걸 letters, recordings and videos.

CBS News contributor Jamie Wax sat down with Apatow and Shandling's fellow performers Dave Coulier, Penny Johnson Jerald, and SNL alum Kevin Nealon. They are are all featured in the film and called Shandling a friend and inspiration.

"He was doing what we aspired to do and he was doing it well. He was – his craftsmanship of his jokes were amazing and his performance was great. And wanted to be like him," Nealon said.

"Everything Garry created was crafted with a certain tip of the hat towards his own vulnerability. And that made him extremely likeable," Coulier added.

That vulnerability is seen throughout Apatow's documentary. 

"Working with Garry was always very difficult because he was as brilliant as anybody's ever been in comedy writing," Apatow said. So if you were writing with him, you know, it would be like tryin' to paint with Picasso. And Picasso's like, "Why are you usin' red? I'm like, 'I don't know. I thought red worked here.'"

Apatow's admiration came early. He was just 16 when he scored an interview with the comedian for his high school radio station.

"I was obsessed with comedy, and hunting down all my heroes to meet with them, and talk with them when I was in high school, and Garry was somebody that I really looked up to, even then," Apatow said.

He got the idea for the documentary after creating material for his funeral, material that went beyond the comedy Shandling was known for.

"Even though he struggled, his real focus was on being a better person, being a more loving person, being there for other people and it moved people, deeply in a way I had never seen before and I thought that there's probably a way to make a documentary that could inspire people and move people in the same way," Apatow said.

After his death, Apatow learned about the stacks of journals Shandling left behind dating back to 1977.

"I wasn't overwhelmed. In the beginning it was very hard to just listen to him just as a friend, it's hard to watch everything and dive deep into his head," Apatow said.

He wrote in one entry: "Your strength now is to move on to live moment-to-moment… That is discipline – it will require strength."

The material helped provide a rare glimpse into a public figure's private reality including how major incidents, like the death of his brother, shaped his life, influenced his creativity, and even affected his ability to trust.

"For me it was just so interesting thinking, 'I never knew this about Garry,'" Coulier said. Added Jerald, "But it's also like Garry's joke when he says his friends tell him that he has intimacy problems, but they don't know me."

Shandling spent his life trying to master his craft, but in fact the secret to his success may have been something you can't acquire – something you peel away.

"I think Garry taught us all and leaves with us all the freedom to be naked. And the ability to be able to laugh at yourself," Jerald said.

"I look at Garry as an innovator. Not only with his standup, but what he did for television," Coulier said.  

"He taught me that real comedy comes from truth. Being honest," Nealon said.

For Apatow? "I think basically what he was trying to say in all of his work is that people should love each other and take care of each other, and be kind. And when they aren't, it's funny."

The two-part documentary "The Zen Diaries of Garry Shandling" premieres on HBO Monday, March 26.