You do not need any special treatments on the baffle face itself. The sound traveling along the front of the baffle will be cancelled by the sound traveling along the back of the baffle (they are 180 deg out of phase) creating a null in the plane of the baffle. This is how the dipole figure 8 sound radiation pattern is created. At low frequencies (<100 Hz) any material you place on the baffle will not be effective.
Sound is not reflected off the baffle.