I would hit it with a strong degreaser, but you have environmental concerns to deal with if it spilled onto your driveway. Most places wouldn't think to kindly of you spraying Westley's all over the ground.
You might try the old soap and good scrub brush routine, just to see if it works. If you have to step it up to something more powerful, then at least you gave it a try.
I'm guessing from reading your other post that you are using this stuff on the paint of your car. Can you tell us more about it, I'm curious. Maybe a link to it on the internet here..I haven't heard of the stuff before.