The stepmill can be an intimidating machine, but if your gym has one, it is a machine you don't want to ignore.
It can torch as many calories as a steady jog, and is perfect for sculpting because it takes your legs and glutes through a full range of motion.
Be sure you are choosing the stepmill, not a stair stepper. The stepmill is the one that looks like a moving staircase. If you do not have a stepmill in your gym, you can still apply the intervals below to a stair-stepper workout!