I'd be loathe to put scotch guard on my kilt (tradional short) but there's heaps of alternatives about. I'd be inclined to approach a reputable travel outfitters and get some insight as to what works and what doesn't. when i say travel outfitters i mean hiking shops etc. Found this product just then having a qick browse for you:
http://www.altrec.com/shop/detail/18867/
don't know anything about it although it seems alright. or should i say seams...