I have given up putting kilts into the washing machine, even those which are made of a machine washable fabric.

The agitation tends to wear the edges of the pleats, and the length of the fabric seems to make it likely to get damaged on the hem or edge.

This only really became apparent after a couple of years, so if you are going to make and then throw away on - say - a yearly basis fine - otherwise I'd say hand wash. I have a separate spin dryer and find that the sturdier kilts are fine in that as long as they are rolled into a cylinder and coiled around the drum. The all wool ones are rolled and squashed inside towels, mostly because they are washed upstairs and the spin dryer is downstairs, but I would put them into a pillow case or wrap them up in a bit of sheet for protection before putting them into the spinner, and for a short spin only.

Here in England - on the South coast near the sea, it is often humid, or raining, and I like to get things as dry as possible as quickly as possible. Things which are left damp for a couple of days can develop a rather musty smell.

If the fabric is really likely to fly, you could try using it double, securing the two layers together on the underside of pleats where it is not likely to show, or use a good length of fabric, lots of pleats, and sew a tape or ribbon to the edge on the inside, use a toning colour a bit darker than the overall colour of the kilt, so as to weight it down.