Agreed, you want the brush to match the exact controur/size of the com. The Fussy Brush gets the contour within a few thousanths of the actual com. You may still need to do a breakin but for a much shorter period of time. With less breakin time you get less comm wear and a more efficient motor for the race.
BTW, this wasn't a sales pitch. I am not afilliated with Fussy Brush other being a customer.
Team Kyosho, Orion, KO Propo America, Avid RC