I bought some glass coffee mugs from the dollar store, cleaned them with rubbing alcohol, let the kids paint them with 4 colours of Americana multi surface paint (michaels) let set for 4 days then bake at 350 for 1/2 an hour. Put glass in when oven is heating and then when baking is done leave glass to cool in oven with the door open (and oven off) The kids painted theirs today and they look awesome. Also, put some tape around the rim so the kids don't paint it (where mouth would sip) I did a test mug and put in dishwasher on top rack and it came out with the paint on so baking makes it dishwasher safe.
Take tape off right after you paint it. Do not bake with tape on