ETL, I’m not sure there would be a way to quantify how much dirt they have. Easiest way is the scene in, Training Day, when Alonzo(Denzel Washington) gets Ethan Hawke to smoke the LSD, laced joint. He’s in the club, whether he wants to be or not, at that point. Some of their dirt was gathered from willing participants. Others, who realized, too late, that they were in over their heads.
Very much like doing business with the mob. Once involved they got you by the you-know-whats.