You're right. He did act as an advisor and played a cameo role.

He first kills the Union guy with a silencer at a parking lot, then the suitcase guy in South America.

I think you also see him in the beginning of the film, standing next to a car in front of a hotel as a guard.

Frank Marino was indeed loosely based on him, if I remember correctly.

"It was between the brothers Kay -- I had nothing to do with it."