Everyone has their theories and techniques... mine in regard to smoothness, is: smooth inputs = smoothness and ultimately speed on the track. Even while at the limit, smoothness in the cockpit is what makes for consistently fast laps.
Take a look at this video of Sebastian Vettle's pole lap in qualifying earlier today at Valencia Spain. I just finished watching this on TV, and this is the only version I could find on the Web. I'm sure others will pop up.
This is a lap record of 1:36.9xx, the only lap ever turned on this track in the 1:36s. You'll notice that except for two pretty big - and necessary corrections, and the few places where he's having to fight the wheel a little when he's up in the curbs - his inputs are smooth as silk.
http://setbyspeed.blogspot.com/2011/...ncia-2011.html