Recently I found several entries on Pinterest referring to painting mugs with sharpies. These made me wanting to try painting mugs myself but I wanted them to be dishwasher safe (I read the sharpie painted ones aren't). For my mugs I chose the Hobby Line PorcelainPEN I bought at a local craft store. It looks and works just like a marker, but it's dishwasher safe after baking.
Clean your mug before painting to make sure the ink will stick to the surface. Prepare the porcelain pen if needed (I had to shake mine for 3 minutes). You should also have an idea for a design by now, mine was the result of some random doodling during a very boring lecture at university.
I recommend to start painting at the top of your mug for a design like mine. Start with the main design (in my case the leaves) and built the rest up around it. This will allow you to be flexible if anything doesn't work out as you planned it. Make little dots for orientation. Small mistakes can be fixed by simply scratching off the paint with your finger nails (it dries after a few seconds). If you have bigger accidents, remove the paint with nail polish remover and a cotton ball.
Let dry at least 4 hours.
Then put your mugs in the oven and bake for 90 minutes at 320°F to set the paint. If you don't use a Hobby Line PorcelainPEN like I did, please read and follow the instructions on your pen!
After baking your mugs are ready to be filled with nice hot chocolate! And you can put them in the dishwasher afterwards!