Short trips with the harness are the best way to go at first, perhaps 10 minutes at a time, working up gradually. You'll have to keep your eye on her at all times and be alert for any signs that she's panicking and overwhelmed, but the walks will get longer over time. We've become known around the neighbourhood as "That eccentric couple that walks their cat everywhere", but with busy roads all around us, there's no way we'd let ours wander around on her own. I don't know if we'll be able to walk the new one yet, I suppose when he sees that Taffy gets to go places he'll get the idea quickly enough.
With a dog, you get to decide where to go. With a cat it's more of a collaborative effort. The cat decides the general direction of travel, but you get veto power over things like other people's flower beds.
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