Best way to remove old grout from porcelain patio

You should use a good sharp blade to cut the old grout then use small hand tool to pull out old pointing before you wadh off before repointing

There are several ways. You can get a handheld grout raking tool. Although this will take some time. Best solution is a multi tool with a tungsten carbide raking attachment. Start the multi tool on low speed at first then gradually increase as you get used to it. I like to finish off by vacuuming out the joint voids. Hope this helps

With a hand held tool and take care when doing the job to prevent and damage

The best way would be with a sharp hand tool, always scrape away from your body as we don't want any cuts to yourself.