I was always that CFI they gave the "this guy can't fly" students to, and with some proper care and feeding, these students always passed their check rides the very first time out. My attitude is that the airplane already knows how to fly, I'm simply going to teach you to guide it.

Everyone learns at a different rate, and usually the regular laws of learning such as the law of primacy and the law of exercise work well. Sometimes you need to crawl inside their head. When a student is standing their in operations with the control yoke still in his hand, with the wires dangling from the PTT switch, there's obviously something else going on in his life.

The mock check ride is a great idea, just call it training as this tends to reduce the threat level somewhat.