Don’t use any chemicals. This could ruin the paint job, or even worse, the gysum underneath. I’d recommend a damp cloth (wetted with water only) and very gently, carefully, try to rub the splotches off. Another thing you could try is putting warm water on the cloth and holding the warm cloth on the splotch for 4-8 seconds and then gently try to scrape it off with your finger nail. Water can be bad for Windstones, so proceed with caution.