Here the template is installed for the top of the airfoil, since this is a small wing I can cut it myself and control the wire speed so the wire enters and exists the foam at same time. On larger wings I use station numbers, maybe 30 equally spaced on each template, I control the cutting speed on the root, my wife follows on the tip as I call the numbers. Be sure to press down on the template as cutting progresses, pull the wire smoothly through the foam and let the wire cut, maybe 2 pound pull on each side. Notice the the paper clip on the trailing edge, this stops the wire as it exits, the wire will bow as it cuts through the foam, it will exit at templates before the center of the wing.
The second photo shows the opposite side, a small wood strip to prevent the block from moving once cutting begins, and weights keeping the block straight on the workbench.