I have always sanded with the run of the grain, since the paddle runs accross the soundboards opposite the grain then if you sand with the grain you increase the drag and friction. If you were to sand accross the grain, looks like you would be defeating the purpose of the paddle's job, to grab. I know from using straight grained wood such as purpleheart or paduak, sanding with the grain increase the likely hood of running the caller softer...just my opinion..pappy