It's going to be a b***h. I haven't tie dyed a kilt, but if supervising about 80 kids doing it (and myself, of course) tells me anything... beware. I would look at dye patterns for ruffled skirts, or anything full of winrkles, crinkles, folds, bends or anything similar. Reason being you want to be aware of what will happen to the inner pleats. Apron will be a breeze, since it's basically a flat piece, can work any sort of pattern in (single/multiple spirals, concentric circles, etc...), but the pleats will be tricky. Again, make sure you get the dye well into every fold and cranny (triply aware of pleats). Oh, and see what research you can get done on the fabric and how the dye will react!!!

I will hit up all my artsy craftsy friends for information on good dye brands, patterns, websites.

Best of luck!