I purchased the goblets at Dollar Tree for a $1.00 each. I used a glass paint, and although the glasses look fine, are a little streaky because of the character of the paint. For ease of use, I would prefer regular acrylic paints, they give a denser consistent appearance, and then add a gloss. Be sure to follow directions with paints, some glass paints should not come into contact with the food. Painting on the outside of the glass should be fine.
All the paints, acrylic and glass require treating the glass first.
As you can see, I kept the painting simple, but stenciling, sponging, stamping, decaling, anything you can do to a wall, card, or sheet of paper, you can do to the goblets.
I have washed these glasses three times in the dish washer with relatively few problems. In fact the only problem was that the heat seemed to loosen the paint, and cause it to bubble off the glass. Don't touch the glass, let it cool, and it will go down, and be fine.