The best way for a bodysuit is to buy a flesh colored one and airbrush the color on.
I googled copper bodypaint, and apparently they sell liquid latex in copper. Warning, there are some skimpy girls...http://www.amazon.com/Mr-S-Leather-L.../dp/B002KIS9CG
If you're totally set on painting, I would suggest Mehron bodypaint or aquacolor. http://www.fxsupply.com/kryolan_catalog/aquacolor.html
You're going to have to have at LEAST 3 colors. One being the base color, one for shadows, and one shiny paint.
Baby powder will NOT stay on, it's a powder is white, it would be too flaky and easy to rub off.