In general there should be very little need, baring a nasty spill, to wash a kilt. Most of the dirt and grime should be removable with a good clothing brush and an occasional streaming. The cotton (or silk) linings one can clean with a bit of soap, water, sponge and microfibre cloth without wetting the kilt. If they are too filthy to be acceptably "cleaned" in that manner then they are probably best replaced. This logic is not specific to kilts but even suits (some of the current fad Super 160s are, despite cost, almost uncleanable) and coats. Dry cleaning does have its place but its for when it really need be (due to environmental and health issues current dry cleaning is moving away from perc towards less effective solvents). I mentioned here the Electrolux Lagoon System (water based) and its, I think, got in theory (as I've not tried it) the best solution for our kilts.