It has been traditional for the Fremont Solstice Parade in Seattle to be led by a cadre of bicyclists. It is also custom for the bicyclists to be naked and body painted, a situation that causes annual delight and anxiety for parade organizers and authorities alike. Nudity is not officially sanctioned, however, no one is about to stop the cyclists. So, the festive and colorful start to the parade continues each year, as dozens of body paintings ride out to begin the event.
The body seems to fall into two schools of thought in body painting. In the first, small designs are painted all over, leaving an effect like the old time stickers on a traveling suitcase, much like the same way designs are applied in Western tattooing. The second school of thought involves the body as a flexible canvas, a surface that just happens to be shaped like a human being. In either case, a large bold design or effect has the best visual aesthetics. 
Water-based stage makeup has evolved to the point where it works well, is reasonably affordable and available more readily. It can be applied with sponges or brushes when doing larger areas, and some brands can be thinned and airbrushed onto the skin. Friction and surface sweating are the two biggest factors when considering how long your designs will hold up. By using water-based makeup, a wide range of colors should be readily available, most people should be able to tolerate it without adverse skin reaction, and it showers off at the end of the day. 
Fancier and more complex makeup is available if you are willing to invest in the product and learn to apply it well. A second person to paint your back and anywhere else you can’t reach is very important. Having a practice session or two can be invaluable when trying something for the very first time, or when you want to do something more elaborate very well. Have a comfortably warm and private location for doing the actual body painting. You will need appropriate clothing, as part of your outfit or, as a cover-up to go to the party or event location once everyone is painted.
If you'd like to learn more on this topic, you might like
Body Painting: Masterpieces by Joanne Gair
by Joanne Gair
Body Painting Kit: All You Need to Decorate the Body Beautiful
by Sophie Hayes
