After doing a bit of research, we figured out the best way to make sharpie mugs. Basically, one should follow the instructions given here:
If you don’t want to spend time baking them, you can print the drying/baking instructions and tell everyone to bake their mugs at home. One of our teens did not wait 24 hours for the mug to dry before baking it, and reported that the colors changed, so the waiting is important.
Have fun making mugs!