@allhyundaicar buddy i don,t use magnetic lasso because its bit complicated i usually use polygonal lasso tool its easy and simple to use , just give it a try .
its on the 2nd place in the pic
You can select the desired area with any tools available, pen tool, lasso or quick selection . make a copy of it Do the painting or use color re-placer or air brush then merge it with the best possible way.
It require some skills to be work with quick enough.
The Nano is looking too much weird with the grille.I think to fit the grille the front needs to be completely redesigned.Also as said by 350Z,what is the sue of grille?
He he, it looks like nano has grown a mustache.For the front grille to be made for nano, you have to tweak the grill to come in the bumpers, I don't know to PS, it, give it a try know? Drag the bumper little downward and then try to add grille