One of the things I neglected to mention in my banquette-building post was how to cut the foam. Having no money, I cut through five-inch-thick foam sections by making repeated swipes with a cheapie utility knife like the one above. It was time-consuming, messy, far from accurate, and doing the curves was a real pain. It's the dumb way to cut foam.
If you don't have that kinda cash but have some building skills, check out this awesome DIY foam saw by YouTube user Designsbyg. You'll kick yourself when you see, midway through the video, what he actually used for the cutting device.