I'm just advancing a hypothesis here, based on my experience, so feel free to shoot this down...
You will probably never be able to change your rate of stubble growth. That's down to genetics. But what you could try is changing your pre-shave routine. Hear me out...
My habit of a lifetime has always been to shower after shaving, since I need to be sure that soap is properly rinsed out (otherwise irritation). However, during lockdown 1 (and only, in TAS), I did explore doing it the other way round for a month. The experiment wasn't really a success, in that I found it appeared to soften up my skin more than my stubble, so I ended up spilling more claret in a month than I ordinarily would in a year.
So my pre treatment is just a good splash of water, as hot as I can stand, from the sink. This seems to help also on those rare occasions I feel the urge to "top up" my shave for the evening. I'm guessing there's a possibility this might help for those with a slow-growth issue...
Maybe we need a dedicated pre-shave thread?