I worked German bred Shepherds, but really liked and always intended to try a Belgium Malinois for their courage and high drive. I was a member of the United States Police K-9 Association, and certified and competed in Region 5 which is New Mexico, West Texas, Colorado, I believe western Oklahoma, and perhaps Kansas.
In 94 I was 4 points off of First Place in Colorado Springs, Co, at the Air Force Academy Stadium, and made the Nationals at Ft. Lauderdale, Fl. It was in Patrol Dogs, and mine was not only a tracker, but was cross trained in Narcotics. What we, and perhaps you called a "Dual Dog".
My dogs were trained by me from pups, I evaluated and with no prior training of any kind, as I wanted no bad habits to overcome. They were trained in evidence recovery, tracking, area search and apprehension, handler protection, criminal apprehension and I was very big on obedience. I have sent a dog after guys that would intentionally run thru crowds of folks trying to mix his scent. Never worked. The dog was never fooled.
My dogs and other handler trained everyday on something, and it always paid off when you needed it. On a bet with a CA, my patrol dog once found a dime on a well travelled Court House lawn. I told the CA to throw the dime, or the dog would track him to it. We weren't allowed of course to be there, when it was throw, and were told only the general area, which was which side of the Court House. Took about 3 to 5 minutes to find.
I was once called in by the Rangers to do a crime scene evidence search in a wheat field where a Texas Trooper was killed. My dog found two chrome buttons off the trooper's uniform shirt. I still have the news film footage of me and my dog going into the field looking for the perp. Him without his collar, and me with an M4, and some rather explicit encouragement.
My K-9s were the best partners I ever had. We could search a Wal-Mart super center together in about 20 minutes from start to finish. Him with his nose and courage, with no power to the building and me backing "him" with a gas operated shotgun. If the perp was there, he got bit if he didn't get up on something.