Hi @Mazatron,
A warm welcome to the Bunnings Workshop community and thank you for your question.
Due to the porous nature of granite and sandstone, I'd suggest avoiding chemical strippers if possible and using tools that won't scratch the surface beneath.
I'd suggest using a heat gun alongside a plastic scraper such as this Pro Renovator 100mm Plastic Scraper. The granite is great at absorbing heat, but the paint isn't so with some concentrated heat, the paint should soften and bubble, allowing you to scrape it off with ease.
Make sure you wear gloves and long protective clothing when using the heat gun and only direct it towards the paint you are looking to remove. These things get much hotter than you think, so don't touch the metal tip as it can and will burn you.
If you aren't confident with this method, you could use DIGGERS 1L Paint Stripper with the same paint scraper, but I'd suggest doing a test section before committing to the full area. If you use a paint stripper, ensure you wear gloves, long protective clothing and a mask and ensure the area is well-ventilated while in use.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
