Hmmmm....tempering cane...interesting idea. Personally I try to use the
least amount of heat that I possibly can on the cane (or reed). There's also the possibility that too much hot air will build up inside the cane and make it "pop".
The only heat treating I do is on reed: the natural wax on the outside gets really glossy when exposed briefly to heat. I use a heat gun, by the way (unlike a fire, there's no smoke....and no irritated eyes
).
I too have noticed that cane and reed will "remember" it's natural shape when exposed to heat (after straightening). Heck, shoots will do that too sometimes.
The only arrow wood I'll temper is hickory....and only on the sharpened wood tips. I've tried tempering privet, but it just gets brittle.
Oh yeah, I never use grease, oil, or whatever. I think that the grease will make paint less likely to stick to the shaft. On cane and reed, I scrape off the natural wax in the area(s) where it will be painted.