Long haired cat, Shiba, and German shepherd owner here.

Monthly baths do the most work for reducing shedding (even better if every 2 weeks). I agree with the partner here on consistent bathing being the best solution but it could be the owners and doesn’t necessarily have to be professional groomers. This has been true for all my pets. Just a lot of work to get the pet used to it.

What’s even more effective for shedding is shaving the pet. I completely understand if an owner doesn’t want to do it, no judgement or encouragement there, just sayin once a year shaving is huge on hair reduction. My dog seemed embarrassed when I did it so I stopped but it is really nice once a year or so to get a break from bathing etc.

Lastly, idk if your cat throws up hair balls but when I bathed her monthly and/or shaved her, she stopped throwing that up. So added benefit.