How does Cubbah disguise himself in order to identify Berryman in the novel, The Thomas Berryman Number?

Cubbah meets Weesner in a bar and has a few drinks with him, making friends. After Cubbah wins Weesner's trust, he takes him out to his car and kills him. Cubbah then takes Weesner's uniform and uses it to get into the circle of security following Horn around on the Fourth of July in order to be able to identify Berryman when he kills Horn.