Best way (slow): Wait until it melts by itself in the spring. Warm water will work, but you may have an ice rink in your driveway afterwards. If you can clear the wind shield enough to move it into a garage, you can let the snow melt off by itself. Removing some of the top layers first after a BIG snow will help the process. Many garages stay above freezing during the winter and should allow the car to clear overnight. If not, buy a heater for your garage to get it above freezing.
Realistically (quick): For 30 inches use a shovel or whatever for the first 3/4 of the snow pack. Switch to a brush for the rest.
If the car has been hit by THICK freezing rain and you want (or need) to clear it fast, turn the brush over and beat on the ice with it. This should break up the ice and allow you to brush it away - works on windshields too. Don't hit after the ice has broken or you might damage the car. <-- I actually have done this with other cars, but I wouldn't with all the aluminum on my FR-S.
In any case, plan on waxing and/or polishing the car on the next warm day, even if you need to wait until April. A snow brush will ALWAYS leave some scratches, and so will any other method that drags snow across the paint to remove it. It is just one of the things you need to deal with for a car that is driven in the winter in snow country.