How it's done.
In case anybody's curious how you put these whizzbang alternators back together, that's why they put a little hole behind them. You push the brushes back, an allen key is very useful for that, I didn't want to dirty one of my good metric ones so used an otherwise useless imperial one for the job. At the same time you push a something thin (I used a 2mm drill bit) down the little hole and past the brushes one at a time. With the brushes held back it's a rather simple job to whack the alternator back together again.