Only In Australia 12 - Litter Kwitter

An Australian mother has successfully trained her cat, Dougal, to use the toilet using a system she invented called the Litter Quitter. This system involves a three-step process with different colored discs to gradually accustom the cat to using a toilet. While Dougal has mastered using the toilet, teaching cats to flush remains a challenge.

What is the ultimate goal of the Litter Quitter training?

What challenge is mentioned regarding teaching cats to flush?