cutting foam

Hi guys! I already tested out several materials (wood, cardboard and metal) but every time i got stuck at a notches or scratches. Which material do you use for hotwire templates? I could use metal sheets but that would be pretty expensive in the end and i don´t want to spend a whole week in...

noticed there were no tutorials on how to make a hotwire so i decided to help out. Here is a video i made of mine. Enjoy!