How do people make polka dot wine glasses and baby bottles?

There are several different kinds of glass paint which can be used to make the wine glasses. You'll probably want to use Pebeo Vitrea or Delta brand. The Pebeo gives a more stained glass look while the Delta is more opaque. Try Hobby-Lobby or Michael's or w/e you have in your area. A google search for glass paint should give you many places from which to order. Paint as desired, bake the glass according to instructions and it should stand up to most washing, dishwashers, etc.