Hey bud, clay sculpt, fiberglass base, sheet plastic detailing and a world of filler and sandpaper.
this piece will be cast in shore 60 urethane rubber pre tinted red so no paint needed, it will be firm enough to hold its shape but be flexible enough to wear confortably.
depending on how stretchy the rubber is (and of course your waistline) hopefully you will be able to slip it over your hips, if not then there are areas that you could slit in order to make it wider to go over your hips.