It doesn't work with everything, just certain manufacturers/models they're trying to ensure there's a decent supply of 2nd hand in a few years time.
Basically you want the smallest deposit possible, none is best... this is the pinch as if you want out of the car, then you don't want a load of dead money sitting in it for you to lose. Then a guaranteed future value, say 60-65% at 2 years. Your monthly payments will be the balance of the new cost and the GFV @x% interest.
There's websites you can use that basically offer your custom to a load of dealers and they bid for your business.