The iron should NEVER EVER touch the fabric!!!
Use a pressing cloth over the fabric. A pillow case will work well.

And NEVER iron by moving the iron over the fabric. That's what you do to a shirt to remove small wrinkles.
Crease the pleats by placing the iron on and pressing down, hard, allowing the heat to penetrate. Then allow the fabric to cool to set the crease.

If you have wrinkled the kilt, remove the wrinkles by hanging the kilt and using a steamer. The controlled heat of steam will allow the wrinkles to fall out and yet not disturb the pleat creases.