I learned a long time ago to use a dry cloth like felt or wool to erase chalk. Like they use on chalk boards. I also have use a make-up brush (never used for make up). Water will set chalk and smear. It's kind of like if someone tracks mud in your house on carpet. It needs to be left to dry so it can be vacuumed. That has been my experience. As far as marking pencils, I'm not a fan. I tested a couple on a sample block I keep( actually a light and dark). Friend of mine tries to remove the markings as she goes after quilting that area. She also doesn't mark until she knows she is going to work on it within a couple days. I would let it dry then try to vacuum an see if that helps.