"I was going to check it with a cheap thermometer "

If you start with a low temperature, try to iron down a sample, and pull it up. If it brings wood with it, it is fine; if not increase the temperature slightly, and try again. When you can bring wood up with the sample, you are good to go. Make note of the setting, and never look back. For shrinking the material, turn to heat up to full, and move quickly.

Les