Clean the mugs well. Wash and dry them. then use some rubbing alcohol and allow to completely dry, maybe 30 minutes. This is to break down any oils that may be left on the surface.
Draw or trace outline of a shape with a pencil. Pencil wipes off easily but also provides a good guide. You can also use a sticker as a stencil to get the basic shape.
Paint your design. Make sure to mix the paint or paint pen very well. If you make a mistake, you can rub the paint off with q-tips. Some paints are easier to remove if you dip the q-tip in rubbing alcohol.
Let paint dry for 1 hour at least to make sure all layers of paint have dried.
Bake Method: Place the mug in a cool oven. Set oven temperature to 350ºF. Once temperature has reached 350ºF, start timing for 30 minutes. After 30 minutes, turn the oven off. Glass must heat gradually with the oven to avoid breakage. Do not place glass in a hot oven. Let glass cool completely in oven. Do not use for 72 hours.
There are a few different paints you can use on glazed ceramic mugs.