What does Greg later wish he'd concentrated on while making, Rachel the Film, in the novel, Me and Earl and the Dying Girl?

The Gaines/Jackson film “Rachel the Film” is symbolic of Greg’s self-absorption. He struggles to come up with the right way to make the film and realizes too late that he was thinking about himself when he should have been thinking about Rachel. He wishes he had taken the opportunity to ask Rachel about her thoughts and opinions so that there could have been a record of who she was and what she was like before she died.