I have had a lot of success with FK425. It's a quick detailer with anti-static properties that leaves a very nice luster on the car!! Plus it smells good!!
Another vote for FK425, but if you've been dusting twice a day I'm not sure this will get you down to once a week.
As Bence once said FK425 is good but nothing is going to set up a magical barrier and repel dust away from your car. It will keep your car from attracting dust so hopefully you'll notice an improvement. Below are two places to buy it: