I put about 5/16"-3/8" of water in a pan, stand the case up and spin pan and case, heating the case mouth with a propane torch, until I see blue move to the shoulder.  By then, the water at the waterline is sizzling nicely.  I knock the case over, pick it out, put another in and repeat.  I'm only concerned that the water is deep enough to completely cover the case when it tips over.

Bertram cases being what they are, I would say annealing cannot hurt, at worst.

I anneal pretty much the same way with all the cases that I do. Draw a pan of cold water, if you are doing a lot of cases float some ice in the water. Get a propane torch, light it and stand it next to the pan. Now stick about 3/8” into the flame and roll in back and forth. When you feel them get warm drop in the cold water. 
  Do not heat them till they start to glow or turn red. That will over anneal them and shorten case life as surely as doing nothing.
40 Rod

I am not a metallurgist, but I have annealed a bunch of BB cases.  I have also overdone it & softened the heads on a score or more.  How far down do the splits go?  You need to anneal farther down than that to relieve the longitudinal stresses from case forming, yet not so far down that you soften the heads.   

I agree with the pan & water approach, but instead of the pan, I use a bucket with the cases set up on a brick. The bucket full of water is the heat sink.  Adjust the height of water in the bucket so that it is at or just below the distance you want to anneal.  When the brass is hot enough, just tip it off the brick & into the water.   

The 25-20 SS case is so small that I question the need to rotate, but that is a personal choice.   

FWIW, I now have both Jamison & original brass for my SS and no longer need the BB stuff.  I can't remember the new name for Jamison, but if the cases are the same, there is no need to look elsewhere.

I always thought that heating and then air cooling brass hardened it-----brass opposite being of steel in that regard.

I think the intended use of the brass might have a lot to do with how it was made.  About 20 years ago I started using Bertram brass in a couple of Stevens 44's in 25-20. Through the years they have been reloaded up to 20 plus times with not 1 failure.  The loads were all kept low, none exceeded 5 grain Unique or equal loads.  Many were even lower.  By my own testing I found that the Bertram was superior to any older , original brass that I found. 
Updating to this year and playing with a R-2 Lovell Krag single shot I see now that the Bertram brass is not standing the gaff as well.  2 out of 20 primer pocket expansions at first firing and several more at later firings.  Yes, I blame it on soft brass heads but
lets stop and be realistic.  The brass was never intended or sold as R-2 brass but rather a low pressure replacement of a obsolete case that hasn't been available for many years.  At this, at least in my book--- it excels and I am darned glad to have it.