I never use coloured wire on its own. I occasionally use anodised wire for jump rings, but only as an accent, and the colours tend to be quite subtle (and to match with silver extremely well). Even then, I tend only to use them for specific commissions. For most things, I stick to metals which are coloured naturally - with the exception of occasionally using gold fill (again, usually for commissions). I love the look of anodised aluminium for large pieces, but I'd want to do it myself, and I haven't the time to learn, or the capital to add more stuff to my equipment wishlist!

As for wire tempers, I would stick to dead soft. It's pretty easy to work harden the gauges you're looking at, but if you haven't got a torch or kiln (or hot oven) then you can't anneal it. In fact, I would say the chamois trick would harden wire rather than softening it. Bear in mind that heat hardening temperatures are far lower than annealing, and as has already been pointed out, you need to keep the metal at a cherry red glow for annealing, which is just not going to happen without a heat source.

For findings, I try to always use findings to match the bulk of the piece itself. I make most of my own, and always make my own for copper or brass (they're almost impossible to buy). I don't generally seal copper unless it's requested, in which case I use Renaissance wax. I prefer the look of naturally oxidised copper, but do explain to customers how to restore the 'bright penny' look if they want it.

btw, if you're buying sterling wire, wires are a lot more expensive than getting it straight from Cookson's - especially with a freepost on!