I hate folding Dacron.
In an old Dutch kitebook from the 90's there was a solution, I've used that idea to make an even more simple version.
You need two glue clamps and two metal plates, check pictures, I don't knwo the correct English name, and even don't know how they are called in Dutch. I just took a good look around in the DIY-store.
Now, push the plate together like on the picture below. Make sure the gap is 2.5cm exact and as tight as possible (under 1mm for sure).
Now take a long piece of Dacron and handfold the first 10cm. With scissors cut a point, this makes it easier to put it through the gap.
I did 40m of Dacron in about 3 minutes. This is fun!
I did not try this with Spinnaker, but I think that won't work as good. Too thin and not as rigid as Dacron.
Of course, for other widths of Dacron, this is as usable.
Krijn
! Looks simple.