I tried walking the late Louie, with mixed results. I took Andy and Dougy for walks in a carriage designed for safely walking small pets, but never on a harness.
As much as Louie love, love, loved being a part time outside kitty boy, he still determined when that outside time was.
This was a particularly successful walk with Louie. Note that I let him freewheel it. The one time I tried to put a harness on him, it took him less than the time from putting him down on the ground till he was out of it!