Actually, when I turn my car off - the engine temp rises - b/c there's no coolant flowing through at all - but then with time, the engine will cool down - opening the hood helps with this. But this isn't your question...

I think electric fans could maybe help that, but really, if no air is flowing across the radiator, it can only work so well. Fans only do so much, but they certainly do their purpose.

There are other tricks to keeping the temps down, I just don't know any offhand!