I think the ESC/throttle trim solution is just fine, running down alkaline batteries is just the old-school way of doing it so some people swear by it whether it's accurate advice or not. It probably originated with mechanical ESC's without a voltage cutoff, so it was safer to just kill some...
That's enough, and it implies that the desired outcome - reduced resistance in the brushes - has been achieved. Part of the performance gain is from reduced losses in the brushes. This means the motor will run more efficiently, delivering more performance for the same amount of charge, and also...