Some thoughts gleaned from other sources:

You would think a smooth, polished surface would have less friction, In theory a finely sanded surface (think shark skin) is faster as it grabs a film of water creating a thin boundary layer for the moving water to flow against.(laminar flow) In practice the difference doesn't even begin to be measurable when you're talking small displacements like kayaks or day sailers. In the 70'S, the U.S. Navy in conjunction with the UC Santa Cruz did tests on laminar flow for naval ships, The resulting data showed that the true laminar boundary didn't start to happen until 57 knots, way beyond anything with a sail or paddle. Sail boat racing teams (ie Americas Cup) have spent Millions of dollars on hull surfaces in test tanks (textured vs. super smooth) with no definative results. Your best (and least expensive) performance enhacement will be gained by focusing on the fairness of the hull to avoid turbulance.