The Bob Hunt method is pretty much what Fred described. Bob also tells in the video that if you are going to do this a lot, make a sanding jig out of a piece of hardware store variety aluminum angle about 4 foot long. Get some of that long, self adhesive sandpaper strip, 100 or 120 grit, and put it on the INSIDE of one of the angle legs. Carefully cut your sheets along the edge with a good straight edge and a new exacto blade, and make several light cuts. Once you have the edge trimmed up, sand if lightly on you new sheet sanding jig. When all your sheets have been cut and treated, do as Fred describes and you will be very pleased with the results. It can be done with thin CA by CAREFULLY applying it to the seem when laying flat on your building board with wax paper underneath.
Type at you later,
Dan McEntee