. Soak rice for 8 or more hours.It's good if rice is soaked in the night if you are planning to use the paste next day morning.
. Once rice is soft, easily breakable with figures. Then grind it with little water. It should be as thick as Idli batter.
. Paint it with brush to fulfill the rangoli design which you have chosen.
. Also you can use mehindi cone to come up with nice outline to the rangoli design.