Ferrets walk on leashes, its true, but generally a walk with a ferret resembles more of a walk with a cat than it does with a dog. This is not to say that ferrets cannot be partially leash trained, or that no ferrets walk "like a dog", simply that MOST ferret walks will involve you following your pet along a route of their choice rather than the opposite.
If you want to try to encourage your ferret to walk like a dog on a leash, you can try using a spoon attached to a long lever. Place some ferretone in the spoon and lead your ferret along with it. Begin with no more than a few steps between "treat breaks" and gradually expand the distance until the ferret gets the hang of it. Limit training to five minute blocks and begin indoors in a familiar area, moving outside only once the ferret has gotten the hang of walking 'properly' on a leash. Keep your expectations reasonable and remember that while some ferrets take to walking on a leash like a dog, not all do.