Safe time outdoors can go a long way to reducing stress in your cat.
Here is how you train to leash walk a cat:
1. Harness Familiarization - put the harness on your cat indoors. Start with short periods and increase until your cat is wearing the harness comfortably for 10-15 minutes.
2. Maiden Journey - Attach a leash to the harness and start in a safe space like indoors, your backyard or courtyard, for very short (5 minute sessions.)
3. Explore - allow your cat to explore. Do not pull or jerk on the leash.
4. Walk - Choose quiet times/spaces to walk your cat. Loud things (dogs, vehicles, kids, etc.) are going to frighten your cat. You might take his carrier with you for the first few walks so you have a place to put him if he becomes frightened. Call your cat to get him to walk with you.
5. Short & Sweet - keep your walks to 10-15 minutes and carry treats with you to reward good behavior.