I just read about aerodynamic paint in National Geographic magazine (either Jan or Feb 2012 I can't remember). It was basically saying the same things about drag, but that in aircraft around 40% of the total drag in from skin friction alone. Most sources, that I've seen, say 30-50% and over 50% on supersonic planes. With the lower speeds we are working with, form drag becomes a bigger component. I would say surface drag still makes up a good portion, specifically at highway speeds 55+ MPH. I can't find the article,
but this link talks about the Fraunhofer Institute in Germany and their aerodynamic paint based on a sharks skin. They estimate the paint can reduce skin friction drag by 4-7%. NOTE: The talk about laminar flow and turbulence is confusing, just know they are talking about making the whole flow laminar by making the boundary layer turbulent...