There is a difference in Scuffing tires and finishing, re-finishing ( sanding tires ) as for scuffing ( putting a run on them to heat cycle ) that can be done after rolled just so it's before the race, I would want to scuff dirt tires on dirt, to finish, re-finish them keep them wet DO NOT OVERHEAT THEM, I would not use anything more course than 150 grit, and finish with 240 grit.