I wouldnt try to make it oversteer with power only, you'd just ruin your transmission.
There's always the handbrake.
Come up to a corner at a reasonable pace, with your foot on the gas. quickly turn away from the corner, then flick the steering wheel back the other way, into the corner, while letting your foot off the gas. Get your foot back on the gas, and countersteer the oversteer, try not to hit anything.
I'd practice on gravel first, much more forgiving.
My starlet is FAR too easy to get sideways....
Its incredibly forgiving, but incredibly easy to get crossed up.
If you change down a gear without rev matching well enough, it just locks up the whole rear end momentarily.