What brew boy said, except for the router bit (pun, ha.). I snapped a line on each ply sheet, either 6 inches back, 8 inches, 4 inches, whatever was needed for that thickness of ply. I used renn's guide from the book to make the initial cut. Didn't think of using the utility knife to trim, but that would have saved some fillet.
Then I stacked the ply(usually 6 sheet, but as many as

, offset them based on the snapped lines (2 clamps was enough, 3 to be safe), and went to town with 36 grit and a belt sander. I think a power plane might have been faster, but not much. You HAVE to buy high quality belts (i.e. around $3 a belt, not available at lowes), but the results were satisfactory.
For kicks, on my dory, I stacked 4 sheets of 1/2 inch, no cuts, and did one side with the belt sander and one side with sureform. Sureform was faster but a lot more work. I learned that I will always set up a cross cut saw with Renn's guide; even though the total time was about the same (takes time to set up each sheet), using the saw was a lot less work.