The only focus of using a slate mill is to increase heart and lung longevity.Unless you own a mill with a brake.The brake can be used to create more tension on the front wheels which deflects pressure to make your hound have to work harder to spin that Slat mill.
It is not completely like using a carpet mill but damn close.
When conditioning a dog. The more exercises he or she is involved in will bring you closer to what you are trying to achieve.I find walking a dog for hours on end is just over rated.I walk a dog to empty and that's it. Once he or she is empty, we start the serious stuff.
JM2C