I used heavy weight Hymo. I think most kilt aprons need something to keep the sharp folds and puckering from forming and also to spring it back in shape.

Though this is not the source from which I purchased my kilt, here is what the Scottish Tartans museum says about the Buzz Kidder kilt:
"Our line of cotton canvas kilts are made from 6 to 8 yards of cloth (more than enough for deep knife pleats). The material is a 10 oz. weight Army Duck
canvas (the same weight as our light weight woolen kilts), woven and dyed right here in North Carolina. The kilts are hand pleated, and machine sewn."

from: Solid Color Canvas Casual Kilts

Just thought I would post that to show what I was talking about on the canvas part.