I live in part of the world where dust is a very serious issue. I get my car washed and can find lot of dust on body within hours.
Is there any easy and cheap method to clean car body?
There is a product called the California Car Duster which allows you to pull off the dust without damaging the finish. I also found this article on AutoGeekOnline.com which gives the basics of why static electricity happens. It basically states there is no way to get around the attraction of dust to paint, but gives some ways to help mitigate some of the effects. Other than that, washing is your next best option.
(PS: I like the @JuannStrauss suggestion of a car cover as well, especially if you don't have a garage.)
Although its impossible to keep your car clean all the time without effort you can follow the below steps to keep it somewhat tidy avoiding the whole cleaning conundrum.
After washing and drying the car, apply one or more coats of car polish and finishing / sealing wax. You will find this makes the paintwork "slippery" and makes it more difficult for the dust to stick to the paintwork.