If you forget to pack you steamer or iron, like I did, one way to take out some of the wrinkles of a kilt is with the shower.

Hang the kilt so the pleats hang freely, away from the blast of the shower. Turn the shower on with just hot water and close the door/curtain. Leave the kilt in the shower for about fifteen minutes or so.

This will take out most of the wrinkles that have formed in your kilt, except for the very worst. Even the badly creased wrinkles will be lessened using this method, and may even steam out if sufficient time is allowed.