How do you find out who Chronicle columnist and political insider Willie Brown is shilling for as perhaps the city’s top influence peddler? Not by lobbyist disclosure statements, which Brown doesn’t file because he manages his work outside the parameters of what the law requires of those who register as lobbyists. So it’s catch-as-catch-can. Latest example: a nifty piece by J. K. Dineen at San Francisco Business Times about a bankruptcy court decision. It shows Brown was owed $750,000 by downtown real estate developer David Choo in connection with a Transbay towers deal. Brown is settling for $300,000.