I've had a bad time selling my cars, as the usual buyer is always trying to catch a discount even where there is none. They'll try to devalue your car with statements like is mai yeh nae hai woh nae hai yahan pay dent/scratch hai yeh jaga paint hai gari ke etc etc.
I'd also tell you that carfirst is a better option in my opinion. Sold a car to them last year, a car that was 2009 model first owner and carefully kept and people kept low balling me saying its karachi registered. Selling it to carfirst was easy for me they inspected the car, placed an offer which I rejected, then after a few calls from them with a better offer we negotiated to a middle ground which was good enough, better than what people were offering me for my car.
So I'd say you should try their services once, if you get a good offer, their buying procedure is almost hassle free.
Good luck