I started painting baubles when I was at uni and every couple of years I add a new bunch to my stock. They're a good item to have on my craft stalls as they draw people's attention. They usually can't believe that I painted them.
I usually work on at lest two baubles at a time so a layer of paint can be drying on one while I work on the other. I pop on a podcast (usually This American Life) and flick between the internet tabs I have open of images found by googling something like 'winter scene'.
I use acrylic paint on plastic baubles. I've found matt, silver ones are best as they're the closest to a white blank canvas, and the paint sticks better to matt plastic rather than shiny.