Gentlemen - thanks you all so much for your ideas. I know the solution is out there, and it may be poly yarn!
I have in my little kit some Neer hair, Z lon and Hi Vis but am not satisfied with any of these as post material. I am finding that after tying there are always a constant stream of little pulled strands requiring trimming, sometimes pulled out by other hooks while in the box. I wonder if Poly yarn is any better?
I have tried all the other methods too, except the calf body hair. We cannot import calf products into Australia so it is about the only thing I have trouble getting, despite the millions of the little suckers wandering our country, or the two hundred I am looking at out the window right now. (I wonder where I could find some... )
My best results have been with that carpet fibre stuff I mentioned, or by sticking with the traditional deer hair stuff. Neither of these gives me visible colors for fast water though, and the other methods are more on the "fiddly" side for my liking.