Paul--I don't know diddly about veneer, but I just took a piece of 4mm okoume and clamped it to my workbench. Cut a bunch of 2mm deep score lines with a circular saw. Took a bench plane to it and worked it down to just the face veneer. If you don't need a lot (and it sounds like you don't) this might work. I'd practice on a piece of scrap to get your technique down. A very flat surface and a sharp plane will help a lot. Cutting the cross grain of the middle ply is a little rough as is going through the final glue line.

Mike Scarborough
Friendship Kayak