I have notice on my Dyno that the motor is getting better after a few skims and I haven't changed the brushes, but I wasn't sure whther re cutting the brushes would make it even better.
The brushes I have kept in it look fine with absolutely no discolouration but obviously the serations have gone.
Xray T4'16, T4'14 (Wet Car)
Xray X12 2016
wlrc.co.uk (West London Racing Centre)