Ah Hamish, this kilt was not washed in a machine but in my bathtub.
I would NEVER put a wool garment in a machine.

I simply put about 4 inches of water in the tub and mixed in the Woolite. Then dropped the kilt in and let it soak for about 15 to 30 min.
A gentle squeezing to work the fabric and watch the dirt come out.

Then pull the plug and let the water drain as you gently squeeze the excess water from the kilt and re-fill the tub with rinse water.

When the water no longer shows signs of dirt I drain the tub and leave the kilt laying in the bottom to drain for a few minutes. Then roll it in a towel and gently step on it to remove as much water as I can.

I them hang the kilt on as many hangers as will fit and onto a line it goes. In the summer I find a kilt will drip dry in about six hours.

With a kilt like this that no longer has any pleat creases or if the creases are badly pressed there is no need to baste prior to washing.
In fact in this case basting would have prevented the accumulated dirt deep in the pleats from being worked out of all the nooks and crannies.