Shows up as the stenographer for Cerebus when Cerebus is pope. While writing he is shown to be a left handed writer.
He has a voracious appetite and is constantly eating.
We see him walking down the street eating while Cerebus is "catatonic" at Dino's Cafe.
Later shows up as a stenographer working for Lord Julius.
Shows up at the bar along the Wall of T'si when Cerebus is also a patron there.
He keeps his hair long over his eyes because his eyes are sensitive to bright light. (issue 206)
Dave speaks about Boobah
Dave also mentions in a Swords Intro that about issue #20 / 21 he went to Boobah's Stag Party. Or at least the guy who Boobah is based on.