To the OP:
I only started annealing a few years ago and my method is a propane torch and a small container of water.
My guess is that you are close to being perfect. Remember that a fast rate of cooling is nearly as important as the temperature. You want to freeze the alloy in an amorphous state.
I worked in a solder factory for a number of years and saw a lot of similar situations with copper alloys. It was hard keeping 3 shifts running the same amount of this or that, but the quality of the end-product remained high. I once did a study of the annealing of our wire and found a huge difference between the inner parts of a spool and the outer (we're talking 500 lb spools). However, the wire that came off the spool ended up being equally workable.
