After brief basic lessons with local drum teachers, Herb Brennan and Jim Tilton, Deen met with Northwest rock drummer, Tommy Suing, who introduced him to the unique style of Neil Peart, of the Canadian band Rush. Suing worked with Castronovo for nearly two years, teaching him the mechanics of Peart's style of playing. Castronovo fell in love with the musicality of Peart's drumming, and it wasn't long before Suing realized that there wasn't much more he could teach him, as he had accelerated at such an incredible pace, it was difficult to keep up with him. Suing was quoted as saying, "It got to the point where all I could do was teach him how to think and be creative. Skill-wise, Deen had become so far advanced, that the student was better than the teacher." The rest is history.