In the fly tiers benchside, there is a paragraph that mentions Al Beatty's method of knowing which deer hair will flare etc when tied, it gives two examples. Is this an exact science?

I am having problems with my collection of deer hair. I have no idea what animal some of it is from, no idea where on the body it has been cut from, and no idea (without testing it I suppose) which will flare and which I can use for wings. In the article Al says the deeper the dark colouring goes the less likely it is to flare, and the lighter in colour (from the tips down) the more it is likely to flare.

Has anyone any tips for me to identify my stocks? Some of it has really short fur, about a 1/4" to 3/8" long, what is this useful for?