Its called Rev Matching. I do it occasionally when traffic starts pissing me off and I have an opening to fly around.
How long have you had your car? After a while you will learn what RPM the engine needs to be at for each gear and speed.
6th down to 4th is still the safest bet for hurried situations.
Edit: Also depends on your rear gears. I wouldnt do 6th down to 3rd with anything other than 3.31's unless you are going 55 or less.
2012 Race Red GT Premium | MT82 3.31 | HID/Security | Steeda CAI | BAMA 91P | JLT Seperator | Steeda Shift Bracket | Steeda ProAction Shocks/Struts | Steeda Heavy Duty Strut Mounts | Eibach Pro-Kit (Dub) | J&M Adj. Panhard | GT500 Axle-Backs w/Resonator Delete | Ford Racing STB | American Muscle GT500 Black Machined 18x9/10 Nitto 555