Still wouldn't do any good though. What Mars needs is to be spun up. Setting the surface ablaze would really do very little good.
Now, hit it with icy, CHON-heavy comets at a nice angle to impart some angular momentum... that'd do Mars some good. Increase that spin rate and the resulting stresses will put some serious strain on the core, causing it to flex and warp. Before too long (one to two thousand years) and you'll have a properly liquid core. Liquid core-->stronger magnetic field-->Van Allen Belts-->Safer Environment.
There's still the issue of growing things there though. You'd have to start up a ladder. After bombarding the place with icy comets to get water back on the planet, you'd have to do something to thicken up the atmosphere somehow. Starting with lots of algae, lichen and plankton, then moving up to more complex plants slowly. It'd take centuries. Mars would always be in a precarious balance, though, even if you did manage to get it terraformed.