I've been using a mouthwash with xylitol for around 5 years now and haven't had a cavity in that time. I hadn't heard about any concern with ingesting xylitol before reading this thread, but I imagine if it's a problem, a mouthwash would be a good way to avoid ingesting much.
Also it's alkaline in ph, unlike many mouthwashes on the market. Caries need an acidic environment to do their thing, so you want your mouth to be inhospitable to them. Acidic mouthwashes may kill off the bacteria, but they make it a nice environment for any that remain to attach your teeth.
The product I've been using is this: https://carifree.com/product/maintenance-rinse/
Also it's alkaline in ph, unlike many mouthwashes on the market. Caries need an acidic environment to do their thing, so you want your mouth to be inhospitable to them. Acidic mouthwashes may kill off the bacteria, but they make it a nice environment for any that remain to attach your teeth.