Only Changing Rear springs with longer and softer springs will do the job.
I replaced rear springs of my swift with softer springs which are slightly longer than OEM and are made of german wire.
The car front Suspension automatically becomes very very soft , because on lifting the rear side the car weights gets transferd to front.
There is a technical issuse with swift that is it is the only car on road that is lower from rear and higher from front.
This made the car lighter from front which makes its suspension stiff and car will transfer even the lightest bump on road to your body