Just generally and off of the top of my head, so I am sure I am ultimately getting it wrong ...
Brand --> Enjoyed all the 'pleasures of the flesh', etc., that came with it, like any normal red-blooded guy ... but was very observant of what was going on around him (and in him) the whole time. Ultimately, he was in it for the experience. He had no idea he'd be writing about this shit later on.
D. Star --> Tried to come off as crass and take-it-or-leave-it, but was really a closet romantic; with an admitted penchant for excessive-ness when it came to alcohol and drugs. He had no idea he'd be writing about this shit later on, or he would have paid more attention.
Happy --> Sex and drugs and rock and roll, baby ... a true decadent, and fucking proud of it, too. He had no idea about later on.