I need to cut foam cores
or have someone cut them for me.
I would like to try the bow and wire system.
Hands off version

There are plenty of companies doing CNC foam core cutting. Eureka is one. You'll get the best quality that way. I learned to cut cores this year using the Del Brengman design hands off foam cutter. I simplified his design a little, and it works well. With any method that uses templates, your skill as as template maker is the biggest determining factor in the quality of the cores you produce. After that, it's your knowledge of which wire to use and getting the pull weight and temperature right.
If you only plan to build a couple of planes a year, it will be cheaper to buy your cores from a commercial cutter. Just the foam you ruin while learning can be substantial (ask me how I know). But then there's the satisfaction of learning a new skill and doing it all yourself, which is why I did it.